First of all, we don’t know how long the cells were out of a human body. And it is possible that the reason the hair did not grow long, thick, and pigmented because it lost inductivity, which has been the problem all along. Ever since Collin Jahoda first put his own cells into his wife’s arm and produced hair growth they’ve been saying that this only works if you do the switcheroo from the donor area to the recipient area rapidly. In the case in point where they just had some limited success they didn’t do it rapidly and so the positive effect was limited. They haven’t solved the inductivity problem, rather they have only confirmed that the inductivity problem still exists because they were unable to produce thick, long, pigmented hairs most likely because of the inductivity problem.
One thing I will say is that the hair cells may not have to be put right away into the recipient area because when Collin Jahoda first did the initial experiment transplanting the cells from his own head to his wife’s arm some sources say he first cultivated the cells for a day or two so perhaps you can cultivate the cells a day or two before putting the cells into the recipient area if that is the case. One thing is that I’m not 100% sure he really did cultivate them a day or two because one reference I read said he did cultivate them a day or two before implanting them into his wife’s arm while another reference I read said he immediately put the harvested cells into his wife’s arm.