(Revised)
Summary of the current arguments in this thread;
Arguments for Venuzdonoa scaling to the Silver Sea:
1. Venuzdonoa was stated to be capable of destroying all of existence
2. Venuzdonoa has no anti-feats to that statement
3. Venuzdonoa scales to Anos and it was stated that as a Lion of Destruction, he is "fated to destroy the Silver Sea"
4. Anos destroyed Elmide who controlled the Vortex which was called the Great Calamity of the Silver Sea. (Revised) The Vortex is in the Abyssal World at the bottom of the Silver Sea's 99 Layers, so given how the superiority of Worlds are determined by their depth, Venuzdonoa scales to the Silver Sea because Venuzdonoa scales to Anos and Anos destroyed said Vortex.
(Revised) 5. Characters in the Silver Sea have reversed the flow of Order (that Fire Dew flows from Shallow to Deep) in the Silver Sea. Therefore, if characters that Venuzdonoa scales above can affect the entire Silver Sea, then of course Venuzdonoa can as well
(My) Arguments against Venuzdonoa scaling to the Silver Sea:
1. Anos didn't know about the existence of Bubbles or the Silver Sea when he made that statement. What he was referring to as "all of existence" was the World (Militia World) and everything in it.
2. People claim that Venuzdonoa working in Deeper Worlds prove that there are no anti-feats to the statement. However, Deeper Worlds are still "all of existence" as Anos referred to, just like the Militia World is. Worlds (All of existence as was referred to by Anos at the time of the statement as he lacked knowledge of the Silver Sea) can't even survive in the environment of the Silver Sea without being surrounded by a Bubble, as the Silver Sea constantly drains magic power from everything it touches. The Silver Sea and the Worlds in the Silver Sea are not the same thing. Claiming that the statement about Venuzdonoa being capable of destroying "All of existence" also applies to the Silver Sea itself would be equating the Worlds in the Silver Sea to the actual Silver Sea, and they very clearly aren't the same thing. On top of that, Venuzdonoa has no feats even remotely comparable to that.
3. The narrative itself never stated that Anos was fated to destroy the Silver Sea. Parrington, a near-perfect Lion of Destruction did. Parrington's knowledge of the Lions of Destruction stems from the conceptual Lion of Destruction that all other Lions of Destruction (including Anos) are incarnations of. The conceptual Lion of Destruction has no feats of even affecting the Silver Sea itself. In fact, it is completely featless. Moreover, "fated to destroy the Silver Sea" can have different interpretations. It doesn't neccessarily mean that Anos could destroy the entire Silver Sea at once. The only way to determine which interpretation is most likely to be correct is by going off of previous feats in the series. And no feats in the series even remotely support that interpretation. Remember, Parrington himself is a near-perfect Lion of Destruction, and in Anos' fight with him, they only affected a single Deep World. Said Deep World wasn't even destroyed, and you have to remember that there are countless Worlds in each layer, and 99+ layers. No feats or statements in the series support or prove the interpretation of Parrington's statement that Anos can literally destroy the entire Silver Sea at once.
4. The Vortex being called the "Great Calamity of the Silver Sea" doesn't mean that it was a threat to the structure of the Silver Sea itself. All that was stated of it was that it damaged many small worlds. Nowhere was it stated that it affected the Silver Sea itself. You can even confirm this by checking the scans that Eldemade posted in an above comment. On top of that, while damaging many small worlds is an impressive feat, it isn't remotely comparable to the entire cosmology of the Silver Sea. (Revised) The Vortex that Anos destroyed isn't the Vortex in the Abyssal World of the Silver Sea. What Anos destroyed was the Vortex in the Abyss of Craving of the Calamity Abyss World. Despite their names sounding similar, the Calamity Abyss World is not the Abyssal World that lies at the bottom of the Silver Sea's 99 Layers. On top of that, in the story it is stated that only the Great Demon King Zinnia Shivaheld has reached the Abyss of the Silver Sea. In the scans I've provided up above, it states that only Issac (Yzak) has reached the Abyss. These two statements "contradict" because they aren't referring to the same Abyss. I would also like to add that the Abyssal World is always referred to as such. Never also as "the Abyss World" or something else. You can reference the scans I posted above (which make a distinction between the Abyssal World and the Calamity Abyss World) as well as the MGnF cosmology page on the wiki (which only refers to the Abyssal World as the Abyssal World). The wiki scan is from chapter 584.
(Revised) 5. Characters reversing the flow of Order in the Silver Sea isn't equivalent to affecting the cosmology/structure of the Silver Sea itself (ie the Silver Sea isn't dependent on Order). Claiming that it does would be making an equivalence between the Worlds in the Silver Sea to the Silver Sea itself. While it's stated that Worlds in the Silver Sea are dependent on their Order in order to survive, that is not stated of the Silver Sea itself, and once again, the Worlds in the Silver Sea are not the same as the Silver Sea itself. On top of that, Anos disturbing the Order of Destruction in his World by turning it into Venuzdonoa which allowed for resurrection and reincarnation to become easier didn't affect the rest of the Silver Sea. We know this because no one else in the Silver Sea even treated reincarnation as a viable concept. What we do know is that Order exists in Worlds, and that Order exists in the Silver Sea as well. It has been stated and demonstrated that Worlds are dependent on Order in order to function and survive. This has not been stated of the Silver Sea. Assuming that the Silver Sea is dependent on Order just the same as the Worlds in the Silver Sea are is merely false equivalency. Even the Order of the Silver Sea (Fire Dew flows from Shallow to Deep) being reversed simply affects whether deep magic is capable of being used in Shallow Worlds, or if shallow magic can be deepened in order to be used in Deep Worlds. In other words, it only affects the power of magic in Worlds depending on the depth of said Worlds, not the Layers themselves or the Silver Sea as a whole. There is no concrete or implied proof of such either.
Keep in mind, this is just a summary of the points made. The thread itself provides more context to these arguments, both for and against.