Yes because it worked out so well for David Reimer...
I'm not defending the practice, but David Reimer's case is a very unfair comparison.
Reimer had no choice at all in the gender reassignment, as they were brought up as a girl from birth. There was no reason to even believe that Reimer was gender dysmorphic or would ever become so.
Reimer also underwent continuous medical examinations while growing up, which may have further confused Reimer and negatively affected his mental health.
Reimers discovery of their transgenderism wasn't until they were in their teens either, when Reimer was undergoing what amount of puberty they underwent. That's an awful time to learn you've been lied to your entire life in some twisted experiment.
Reimer also discovered that they weren't who they thought they were at a period of time where transgenderism was practically unheard of in the West and there was very little support for transgender individuals. One of the only transgender people Reimer met was a prostitute.
All of this weighed up, I think it's very clear that the odds were always stacked highly against Reimers mental health.
They had no choice in the matter, even if they would only regret it. They had an entirely unnatural upbringing. They were unfortunately born in a time with significantly less mental health support, and little to no support for transgender people (whether consentually transgender or not).
I think it's unfair to assume that a person without all these extra challenges will definitely come to take their own life as Reimer did.
All that said, I absolutely do not agree with performing/giving any transgender surgeries or medicines to minors.
There is no way a minor, particularly one who is pre-pubescent, or only just started puberty, to know exactly how they feel about their gender and identity to the extent that they can make a lifelong decision they will always be happy with.
Letting a young child dress in clothes usually reserved for the opposite gender is fine. Kids will play and experiment, but it doesn't mean they definitely want to permanently change their bodies.