Is Joe Biden still a moderate centrist or has he become progressive on the political spectrum?

A moderate centrist, which is why he was nominated instead of the people more to the left.  If he was a "leftist" as some idiots claim, he never would have been elected.  Luckily, few people buy the nonsense spread by extreme right-wingers who are so far right they think centrists are leftists.

He just signed an order saying men can play on women’s sports teams.    Sounds progressive to me.   

He's been a lifelong political opportunist. Not unlike many politicians . 

Joe Biden, like the vast majority of all Democrats is a centrist, most Democrats don't like the left wing loonies either, which is why there are not many of them in Congress 

Hes an abortionist and a touchy feely SJW, that answers your question fully.