I don't think this reflects reality at all, at least if we define the center they way DC journalists do, which is of course bonkers. Dems run on things which DC considers to be "lefty" (but which do in fact have broad appeal), and then fail to deliver them. They run from the left then govern from the "center" (pick your preferred villains to explain why, but this is what happens).
Biden won election campaigning on a bunch of stuff that would make Bernie Sanders quite happy, and will fail to deliver many of them, either at all or in a functional way.
In 2022 they will run on them *again.* And then in 2024 they will run on them *again.*