> answer seems to be "we don't, he's on the board of a competiting AI company"

That seems like a good reason to listen to him? He is prominently placed in the field. Has a lot to lose by knowingly making false statements in public about a competitor. And has an incentive (and the resources with which) to dig deeply into them in a way e.g. a trash-talking YouTuber does not.

He has his set of biases. But Board member at a multi-trillion dollar established software and AI kingmaker seems like a weird way to dismiss an opinion.