Yeah, in principle it's supposed to help stimulate transition from telogen (rest phase) to anagen (growth phase) and thus stimulate greater recovery of hair follicles once the damaging signals (ie. androgens) are interrupted.
It would ideally be used in combination with an anti-androgen or other agent to block androgenic damage (eg. PGD inhibitor, anti-histamine).
We don't have very many effective ways to stimulate a telogen > anagen transition so this would be very helpful.
Minoxidil is one but it's terrible for your skin in my experience.
Wounding and PRP do this also but in a messy and inefficient way in my opinion. I also worry with these about increased collagen deposition and scarring from long term use, which could then become problematic.
Estrogens in theory can do this through ER-beta stimulation, but my experiments with estriol just left me with eczema and asthma (which are mostly gone again now), so that could hardly be considered a "clean" mechanism. Estrogen seems to interact with the immune system.
If a topical JAK inhibitor can promote anagen effectively without too much other mess, it would be very helpful for maximizing re-growth once you have a good regimen already in place.
I would be very eager to try one if the evidence is remotely decent when the studies are done. We need more growth stimulants. The ones we have are not so great.
This problem and how JAK inhibitors may solve it is summarized here:
Several hair growth disorders are characterized by the inability to reenter the growth phase of the hair cycle (anagen) due to hair follicle (HF) miniaturization. Current pharmacological therapy for androgenetic alopecia is primarily focused on the prevention of further hair loss. However, the search for pharmacologic agents to restart the hair cycle has been largely unsatisfactory. Recently, we demonstrated that pharmacological inhibition of the Janus kinase (JAK)–signal transducer and activator of transcription (STAT) pathway promotes rapid hair regrowth in alopecia areata in both mice and humans (1). Here, we show that pharmacological inhibition of JAK-STAT signaling initiates the hair cycle in normal mice and promotes growth of hair follicles in humans.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4646834/