Will Retin A benefit/improve scar healing at the donor area after FUE?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.   There are no medications to speed up healing.

A-Cell has worked well for my patients in promoting scar healing and minimizing them as well. Most scar medicines like the ones you listed don't have studies to prove their effectiveness. But I don't believe any of them would cause harm, so if you feel as if they may help you go for it.

The use of Retin A in the donor area does not make any sense to me. Retin A is an irritant and will just cause inflammation of the donor area

Moist wounds heal best - so keep the area clean and spray with saline or plain water every hour you are awake for the first three days.  Plain vaseline can help, as can neosporin (avoid bacitracin - allergic reactions).  PRP (+/-ACell) can help, as can post-op healing kits that contain copper peptide solutions.  Ask your doctor what they recommend!Good luck!