It is not specifically about surgeries. If someone changes their name, pronouns, and presentation for three months and then decides it isn't for them, that's a detransition, no surgical involvement. If someone is on hormones for a couple of years, and can't deal with their family being godawful and their job prospects drying up because they're in an unaccepting area and goes back to their old name and clothes, that's a detransition. In fact, the latter case is the most common kind of detransition, where people have to because of social pressures or lack of support. A lot of those people retransition down the road, when they're better able to. Almost nobody who goes far enough to make medical changes regrets doing so.