They are different, yes. However, the nature of hair follicles may make it appear that hair is regrowing when it's not the case. At any given time, only a fraction of folicles are producing hair. They grow it, it can fall out, then they lie dormant for a time before regrowing again. What your friends are likely seeing is new growth from formerly dormant folicles, not regrowth of treated folicles. I think it takes a year or two of regular treatment to treat them all.