Earlier quoted context omitted.
The original author was an executive at WotC, with access to professional legal advice. If they wanted the license to be irrevocable, they would have put it in the license.
If we look at other contemporary licenses reviewed by professional legal advice, like the GPLv2, Creative Commons v1-3, MIT, Apache v1, they all have the same omission of irrevocable, and it was about another ten years before they released newer iterations with that magic language (or didn't, in the case of MIT). It's also not speculation that that was the intent of the original author, they're on record from both th…
Yes, a corporate executive is on record making a claim like that. Do you take it a face value?
This person is a sophisticated actor in a company that runs on IP. It doesn't matter what FOSS licenses said, and I don't have time to look into that. If Wizards wanted "irrevocable", it would say that. Did you see Wizards' attempt to redefine 'irrevocable' in the first revised draft? Same company.