[lexicality]

You need to be wary about what positions people report "trans activists" as holding. The website you link to is considered "questionable" by the Media Bias Fact Check website (https://mediabiasfactcheck.com/quillette/) and The Times has been instrumental in pushing transphobic rhetoric mainstream.

While I'm sure you could find someone on tumblr posting about how all 3 year old boys who play with dolls should immediately be given HRT, all mainstream thought (by trans people and medical professionals) I've seen is that children who exhibit gender dysphoria should be given puberty blockers while thorough psychological analyses etc are carried out.

[throwaway53453]

But even puberty blockers cause development issues in children. We are talking about permanent damage for something that might actually be temporary. Why not just let them decide at 18?

[plorkyeran]

At 18 it is too late and puberty has already done permanent damage. The entire purpose of puberty blockers is to make it possible to defer the decision until they are adults.

[lexicality]

Do you have more information? The only issue I've heard about puberty blockers is a slight reduction in bone density over extended usage which is apparently considered negligible. I'd be interested to read a paper or medical journal indicating otherwise.

EDIT: But also to answer your question - if you think a 10 year old child might be suffering from gender dysphoria but you decide to leave it 8 years to see how things turn out, you then have to spend an enormous amount of money undoing the puberty they went through and performing various surgeries (eg mastectomy).

However if you put that child on puberty blockers and give them therapy, it should become obvious very quickly if they're just faking it for attention and they can be taken off them again.