> puberty is a natural function of the human body
The onset of puberty is way earlier than it used to be. Per http://www.mum.org/menarage.htm, "In 1860 the average menarche happened at 16.6 years,"; per https://www.thetimes.com/uk/science/article/girls-now-begin-..., "Girls now begin puberty aged 9". Delaying puberty until age 16 could be argued as the more natural stage (though I take such arguments 'round back, and beat them to death, especially if they support my beliefs: the naturalistic fallacy is too seductive to listen to).
> That makes no biological sense.
Biologically, there's no reason* we couldn't make them wait until adulthood to begin puberty. You've not quite identified where the ludicrousness is – though you're close.
Past that point, I think you're doing what I did earlier, and arguing against a position I haven't taken. (Unfortunately, I'm less eloquent than you, so I'd spend several paragraphs if I were to correct you: I'll trust in your ability to work it out.)
> the aim should be education of and societal support of parents to be as informed as possible
A thousand agreements: this is the ideal. All other situations are pathological special-cases – though, like antivax parents, they're special-cases that the medical system does have to take into consideration. (I don't know whether you have a general-purpose equivalent of Gillick competence in Norway, but see https://learning.nspcc.org.uk/child-protection-system/gillic....)
This isn't a point I've been trying to focus on, since it follows once correct handling of the ideal "everyone's informed and with the child's best interests at heart" case is established.
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*: Biiiig asterisk here: abnormal pubertal timing is associated with health problems (see https://www.endocrinology.org/endocrinologist/134-winter19/f... and citations), but we don't have solid data on the arrow of causation, nor good data on confounders (social attitudes seem to be a problem in the US, and https://doi.org/10.1542/peds.2005-2939 strongly suggests that social/psychological effects have a big impact on onset of puberty), so that would be a separate point. There are no known problems caused by the use of GnRH modulators to postpone puberty (except low bone density, which per https://doi.org/10.3389/fped.2022.968485 and https://doi.org/10.1210/jcem.87.2.8202 is temporary and goes away in puberty, and per https://doi.org/10.6061/clinics/2012(06)08 doesn't occur at all – and can be ameliorated with calcium and vitamin D supplementation), and afaik there's no theoretical expectation of such problems (except, again, bone density: I'm not sure that anyone knows why that isn't more of an issue, since it is sometimes an issue when GnRH modulators are used post-puberty – though the patient information leaflets I've read still stress the treatment as extremely safe in adults (with more assurance than I'd have given, but hey, I'm not an expert)). For the sake of the thought experiment, please pretend there are no such issues.