This is one situation where I want someone versed in Catholic law and tradition to chime in.
It does seem to me, based on what I know, that it should be possible for a good Catholic (i.e. one follow church teachings) to say that you personally would never participate in an abortion because you think it is a sin, but that it would be wrong for the government to enforce a ban. I am under the impression that Catholics generally support a separation of Church and State.
Assuming this is correct, it would seem these bishops are the ones making noises for political reasons. They are right wing, and are fishing for things they can condemn Biden for. They want to push other American Catholics from supporting him, rather than being genuinely interested in following Catholic teachings.
And yes, the fact that they single out Biden when he’s far from the only public person with this position—let alone all the Catholics who publicly support abortion—lends additional credence to this belief.
But I would love it if a Catholic scholar/legal expert could chime in.