The problem with targeted exam hints on what to study is that it can create situations where a student who understood the material better overall and put in more effort studying all the material equally, scores lower than someone who simply happened to get hints from the professor. If your actual goal is to educate, you shouldn't give exam hints, and especially not one-on-one.

For sure - I think my definition of an exam hint is more like, study these subjects or “yes, data structures of some kind will be tested, but don’t worry about sorting algorithms.”

Not specific hints or answers, that’s obvious favoritism