That doesn't make much sense to me. Let's say if I were interviewed at some place using Java, Python, C and Go, why shouldn't I state my personal language preferences?

For most things as an hiring manager I'm OK with people working with their favourite language on whatever project I assign them to (as long as it isn't too esoteric; OCaml is OK, but Haskell is probably pushing it a bit too far, for instance), except when they have to work on an existing code base, in which case I wouldn't want to hire someone hating it; they'd be miserable and the resulting code would be awful.