In this meta-analysis, the regret rate of GAS was found to be 1%.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8099405/#:~:tex...).
Compare this to:
Prostrate surgery: https://www.europeanurology.com/article/S0302-2838(08)00764-... (19%)
Knee surgery: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6961288/#:~:tex... (6-30%)
Mastectomy for breast cancer: https://www.medscape.com/viewarticle/964824 (8% -- and this is presented as very low!)
The satisfaction rate for gender-affirming surgery is in a completely different league from the rest of medicine. (And I have a lot of sympathy for the few people that do regret them -- I'm good friends with one such person.)