Yes, I know that. The point is that, although different skills can have similar observable effects, they do not necessarily have the same working mechanism behind the scenes. Cancellation, Infinity Spear, PvP ability of daggers and fists, banes, block wind walk, steal divinity might very well have different formulas on which they base their success rate.
So let's return to what you said - which is as follows: because the cancelling effect of certain skills works through invulnerability conditions, and because one of them seems to, empirically at least, not be influenced by Mental Shield, then all of them are not influenced by Mental Shield. Which is not necessarily true, you're establishing false causality. And not only it might not be true, it is likely to not be true - since things have been tweaked throughout the chronicles (the Infinity Spear and the Steal Divinity being the best examples).
And I'm feeling that we're pushing away from the issue. The statistical test that I've proposed is a far better method of falsifying Admin's claims.