Firstly, they're all CBs and are clearly defined as such. Bacuna hasn't really made any position his own because his skillset doesn't really suit any position.
Secondly, Clark and Baker had this said about them despite showing potential to grow into the role and young CBs make errors, it's how they learn. Anyone saying the above about Vlaar, at best, was/is just plain wrong.
I haven't seen any performance from Bacuna that says to me that he can be a good enough first choice Right Back for us. I think his best position is probably as a RM, seeing as his crossing is good.