I think that was the source of the concern when he was hired - many questioned whether he was the mentor or the understudy, and BVS led many to believe we got the understudy.Are you trying to say that Alex Golesh isn't really an offensive coordinator because he has /TE after the OC? Come on, that's just silly. Coordinators often also coach a position group.
As for Co-DC, that can mean many things. It can mean that he's really the main dude, and the other guy is an understudy. It can mean the opposite. Or it can mean anything in between.
I certainly don't know Penn State's situation from 2016 through 2020 well enough to explain how much in the lead role Tim Banks was. Can you? Do you have sources?