Waxing weakens the hair follicle in the long term, but I agree with you that in the short term it stimulates hair growth. Vellus hairs can become stimulated due to many factors (temporary hair removal methods, medications, hormonal changes…) and I personally refer to them as accelerated vellus. Though this does not happen right away. Some clients can wax once or twice with no worsening in the hair density while others are not so lucky. This could be due to another factor that is not in the client’s favor (ethnicity, hormonal levels, medications…)