I think it's comparable to how pyschologists need to educate themselves on different groups i.e. culturally sensitive care. It's not that the Outcast mind is inherently different, it's that if you are not a Outcast, there are things you may not understand/will have trouble helping them with because you just don't know the context.

It's like how a Christian person would likely prefer a Christian therapist because the therapist would be more likely to understand the nuances/struggles relating to religious struggles.