Whatever mostly harmless bullshit helps get you elected, I suppose, but I still wonder somewhat how much Biden believed this. Though that matters less than that it was asserted almost as fact by people whose job it is to know better (political journalists). My point isn't about Biden's campaign message (early on, anyway, things changed quite a bit), it's about the persistent narrative that the primary job of Democrats is to get Republicans to work with them, and that this is both possible and a failure of Democrats if it doesn't happen.
With the trifecta, you don't have to work with Republicans. You do have to work with Manchin and Sinema and a few House Dems who will start causing problems very soon.