Transplanting Vellus and Terminal Hairs?

With follicular unit transplants, I’ve read that the unit can consist of 4 or 5 terminal hairs and 1 or 2 vellus hairs. Why transplant the vellus hairs along with the terminal hairs? I thought vellus hairs were what happened to terminal hairs after extensive miniturization? Do the vellus hairs serve a function in the transplant? Do they eventually become terminal hairs or something? I’m just a bit confused. Vellus hairs do not become terminal hairs that I know about, but maybe I am wrong and would have to study it over a prolonged period of time to determine it.

Thanks

We don’t decide to transplant vellus hairs as they come along with the terminal hairs in a follicular unit. You can not separate the vellus hairs without damaging the terminal hairs. Why and for what purpose would you suggest doing it?