I have never seen a manager complain about the use of functional programming.

What I have seen is amazingly intelligent programmers with FP backgrounds (who I pushed to hire) try to write in languages that are sort of FP (ie Java and Javascript). They end up writing code that is not canonical (which I don't mind) and using academic/haskell variable names (ie single letter variable names which I do mind heavily) and then fail to write any documentation (anecdotal observations).

I'm not saying this always the case but I have seen it quite a few times.