That is more or less a mechanism, but not one that allows to conclude much higher power than plausible, as it doesn't explain how it stops the damage.
Actually it sets a pretty reasonable limit: If it is a divine blessing than it will probably at most hold up to the powerlevel of the divine entity that made the blessing. At least unless some specific higher level is mentioned.
So you can probably argue that it holds up to whatever that god (or other divine being) is ranked as, but anything higher is a NLF.
Intangibility is absolutely different in that regards.
That much can already be seen in the fact that intangibility would be treated as protecting irregardless of power, no matter wether or not it was explained to do that.
That is, because based from the mechanism we know that there is no connection between the amount of power and the character, as the power simply goes right through the character. The work the ability does is the same irregardless of power.
On the other hand when it comes to invulnerability there are various ways that can work.
The most common kind is something like
Jack Elva. It is said to work, but how it archieves the result is unknown. In that case we might as well treat it as a forcefield that blocks all damage for the character (like immunities in Kumo desu ga work for example). In this case we run into a NLF because there might be an upper limit to the power of the forcefield.
Different Mechanisms behind invulnerability can make the ability work, if we just know that it is meant to work that way. For example I recently had a case were a character was immune to blades worse than his own, because he was in a pocket dimensions where he altered the concepts and through them the laws of nature to make it work that way. Given that one can not plausibly break the laws of nature or change concepts through power alone in this case the mechanism does allow to extrapolate for it to work on higher levels.
Point is: You first need to now how it stops the damage. Once you do you can see if the ability might have to invest more effort if the attack is stronger or not. If not, then it is fine to extrapolate and say it works up to what the mechanism implies it should. But if it might has to put in more effort than it doesn't suggest to block against more than the highest showing/statement/plausible implication.
And in regards to the infinity you are actually saying that it works against infinitely more powerful opponents then? Like, High 3-A's and the equivalent for other dimensions?
In regards to the "context of the wiki" thing I would suggest to formulate it a bit different then, in order to clarify it further. Maybe something in the direction of:
Many works of fiction consider extremely durable characters invulnerable, but this ability is only to be added onto a page if it is made clear that to be more than simply high durability and is not contradicted.