This is true for hair loss treatment agents in general. Medical treatment is better at coarsening what you have than at growing new hair. So people with a lot of fine hair to start with tend to do better. Unfair, I know.
I wish that was the case for me Dr. P. Been a diffuse thinner in the front and 10 years of finasteride and minoxidil has never thickened up, just gradual loss.