@whatintheworld the studies you linked above say nothing about the donor area though. The Eugenix video says they believe the recipient area thinning occurs precisely because of thinning in donor area.
Earlier you said that thinning can occur in the recipient area even if the donor area shows no signs of thinning. That is what I'm unsure about.
The point of the video is that there is always "some" level of androgen susceptibility in the donor area.
The recipient area affecting and changing hair follicles is already proven. Look at beard and body hair grafts changing ever so slightly as they adapt in the recipient area. They take on "some" characteristics of the recipient, but still retain most of their inherent genetic programming.
The donor may not show visible signs of thinning immediately. Or it may be very, very slight. Even under a microscope I am unsure if a surgeon could say precisely, this follicle is 100% healthy vs 98% healthy. How would we even know how to quantify such slight differences? I don't think any surgeon would tell you grafts are completely binary, either healthy or non-healthy. It is a spectrum, like everything else.
For most people this difference is not relevant though. Their androgen susceptibility in the recipient area may not exceed the threshold that the graft would need to surpass to be compromised once transplanted. However, this all depends, again, on a case-by-case basis for each individual patient, and what their particular susceptibility is.
This risk, however, in my opinion, is almost 0 with finasteride. You take an already quite resistant graft from the donor, and protect it even more with finasteride, and it should be good for life (just my opinion).