I've seen this sort of claim a lot recently - i.e. that "the same people" are making contradictory arguments over time.
I have no stats to indicate it's incorrect, but I am suspicious of the claims.
Even as someone who spends too much time reading this board, there's only like a half dozen posters I recognize enough, and to whom I pay enough attention over time to notice whether their posts, in aggregate, adhere to some set of consistent positions. But maybe that just means I'm a sociopath?
It seems more likely that we're mistakenly viewing most of the posters on here as part of some fictional monolithic "other", whom we can attack as being illogical and incoherent, but only because we're buying into that illusion.