The error you are making here is presuming consistency.
The Democrats don’t do consistency except where the thing is particularly evil (e.g. abortion, homosexuality, forced demographic change, etc.).
Democrats are outcome-based. The desired outcome is the coronation of Kamala Harris, which was telegraphed by the NYT 2 weeks after Trump was elected. This particular thing is therefore only significant as part of a choreographed triumph over an old white man whose time has expired.
No apology from Biden was ever requested while he was Obama’s second. There was no outcome that would be advanced by it.
Unless the promote-KH outcome is advanced by it, no other will be asked to apologize for cooperating with or voting for segregationist Democratic Party Senators.
I haven’t made an “error.” I am throwing it back in their collective hypocritical faces.