Dysfunctional Rules X: I Cast Comprehend Rules

[glass]

The problem there is: the "... can be slain only by ..." line is blatantly false

It's a rule. It cannot be false (blatantly or otherwise). It can be overridden by more specific rules, but otherwise it stands.

(for example, Regeneration can't save from lack of air - and Tarrasque's Regeneration is no different there)

Sure it is. Because it says so.