Approved source
From the treatment guide.
Chin hair tends to be coarser than hair on the upper lip, which is part of why threading works particularly well here. The thread grips and pulls multiple hairs out from the root in one motion, getting closer to the skin than tweezing and lasting longer than shaving since the hair has to regrow from scratch rather than just regrow a blunt tip.
This is a popular standalone booking for clients managing PCOS-related or hormonal chin hair, since threading doesn't carry the same risk of ingrown hairs that waxing can on this area.