I suspect a lot of it isn't actually coming from real Dems/Progs.

A lot of it is - and mostly from progressives. I mean, the OP linked an article from one the liberal columnists at the Washington Post. That's not a false flag operation - it's not a MAGA-authored piece that someone submitted by hacking his account.

Progressives who only begrudgingly accepted Biden after their preferred candidate (the also-old Bernie Sanders) was beaten want to make it very clear that if he loses in 2024, that they shouldn't be blamed. That it's Biden's fault. Or the Establishment's fault. Not theirs.

Laying that groundwork now is important, because if Biden loses it may very well be because he bleeds support from the base of the party - young people and black/hispanic voters. Progressives will get blamed for that. Not entirely fairly, because black and hispanic democrats tend to make up the more conservative part of the party base...but even so.