> Section 2 of the GPLv3 explicitly declares itself irrevocable provided the terms are complied with.

Yes, it does say that. That doesn't actually override a law which makes it revocable at will irrespective of it's terms—the license is governed by the law, not vice versa.

Whether the GPLv3 is a gratuitous license probably depends on the circumstances of licensing in a particular case and not the text alone—its certainly possible for it to be a contract license instead, but it's not, AFAIK, clearly one in the general case.