It's literally something that helps maintain a physical aspect associated with a person's gender. Granted, hairloss can happen to anybody, but baldness is highly predominant towards the male population.
Many men aren’t happy about balding, especially earlier in life. They feel distress at their body not presenting the way they want it to (with hair!). hence, gender affirming care.
I've never heard anyone argue that men with no hair loss are less manly so no I don't think it counts as gender affirming care.
I have man boobs, I guess fixing that would technically be gender affirming care because I'm embarrassed of having female features, but balding is really a stretch.
But male pattern baldness is a male trait. So to affirm, wouldn't it be more of this? Men getting their hair follicles removed to emphasise this male condition.
It doesn't really make any sense to say that preventing a natural feature of men from progressing is being done to affirm men.
It's called "male pattern baldness" and is caused by androgens, counteracting it would be 'less male'. And that's without mentioning the social aspect of focus on appearance, which is generally feminine-coded.
