I honestly can’t believe that on a so called feminism forum that I’m having to explain why women should be allowed autonomy over their own fertility.
I actually agree with what you have said about the vastly different impact of reproductive role on men and women.
The need for women to be able to control their fertility is, I think, the most obvious sex based right and why it is so important that sex and sex specific rights are recognised in law. I'm so glad that you understand this.
However, that right is not absolute. A pregnant woman cannot demand an abortion at any time.
In the specific case of sterilisation, doctors are allowed to balance the consequences of giving irreversible treatment to somebody who may later regret their decision, given that other forms of long term but completely reversible contraception are available.
But even if you think the balance is wrong in both these instances, it still doesn't follow that GNrH antagonists (no evident of benefit, clear evidence of harm) should be prescribed to prevent puberty, because that is a completely different treatment, and the judgement needs to be made on completely different criteria. It's really not clear why you would conflate two such different things, and calls into question whether you are arguing in good faith.