I can't imagine anyone as forthright and astute as Dave was unaware of TOS dictating that posts made are the property of WBF. So I'd assume Dave being surprised he can't take his posts with him, or delete them, is not the reason for his self cancellation.
No, I think we should just take what we've heard at face value, he doesn't believe he should be moderated, and maybe his dislike of the individual moderators is extra spice.
And if you don't believe you should be moderated, and you are, well then you head for the exit door, how hard you slam it behind you is your choice.
My thought? You can certainly disagree with the reasons you've been reprimanded and argue your case.
But to maintain the position that you're above moderation and all that entails, is just preposterous.
And unlike those in the public eye who are truly in the firing line of genuine cancellation, again there's no parallel here.
I don't see JK Rowling cancelling herself despite the unrelenting hordes online, but Dave has cancelled himself, first chance he got, with not even a whimper.