I’d say around a quarter of patients see full growth at 18 months. About the same amount that see full growth by 8 months. The vast majority see full growth by 12.
I think it's possible he did some minor work. But it is also possible that he's on some form of dutasteride mesotherapy treatment. HIs hair looks thicker than it did 10 years ago, so he's definitely doing something. Although it may not be surgery.