That is interesting but the same study also says that 21.7% of this cohort disengaged from the clinic. So the rate could be even higher, depending on if they stopped treatment entirely or changed to another service provider.
When an elderly person rejects knee replacement prior to surgery e.g., because they’ve learned the risks, they’re also not counted in the regret rate for knee replacement.
EDIT: Those that disengaged did not complete treatment, therefore they cannot regret completing treatment. Perhaps they regret starting treatment and perhaps they don’t; either way, that’s not the same thing as detransition. I can’t read their minds to figure out why they disengaged, and neither can anyone else.