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
(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.
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.