You and your hairdresser are going to enjoy this:https://hsci.harvard.edu/goosebumps-hair-follicle-stem-cells#:~:text=It%20secretes%20a%20protein%20that,regenerate%20the%20new%20hair%20follicle.

I've experienced the same thing, and I don't even have a hairdresser! Hair regrowth on my legs, arms top of my head. My wife says on my back where I never had it before!

It's driven by the sympathetic nervous system! Not the parasympathetic, tho I suspect the 2 have to be well-balanced.

as a 43 year veteran of hairdressing and the ability to control my goosebumps i can tell you now 100% theres no correlation between hair growth speed , and this phenomenon