The problem is that the order extends to puberty blockers, which are a safe and reversible treatment for kids to keep them from maturing into their undesired gender until they're old enough to opt into more drastic treatments like hormones and surgeries... or not, as they choose.

Edit: also wtf does that have to do with sex? Do you mean the larger subject of child consent in general? Because contract law would be a less extreme example of children not having power of informed consent.