In my view KJK is someone who is very brave and at the forefront... but if anything I believe we should take a slightly harder line than she advocates for.
I do not agree with the tweet, I do not think anyone should tweet it and it looks like KJK didn't tweet it.
However, you are right.
A woman claiming to (want to) be a man and taking testosterone is -
(1) At risk of sterilization whether she wishes to be sterilized or not
(2) Presumably not wishing to get pregnant, ever. Pregnancy is as womanly as it gets.
(3) Presumably not wishing to ever have PiV intercourse, as this is almost as womanly as getting pregnant.
(4) Presumably (as a result of 1-2 above) not even slightly concerned about the possibility of being sterilized.
So overall, one might argue that in term of the tweet's precise words, which say nothing about forced sterilization, the message is really not that bad at all.
Then we get onto the serious issue - what does testosterone pre- and during pregnancy do to the foetus, and in turn to the child / adult.
It seems to me that the risks to the child are potentially very high, with no possibility of an upside. Given that a fair few kids must exist now, it would seem to me that we should (ideally) see no more trans'man'-on-T pregnancies until the current cohort of kids have reached 20 or 30 years old and been studied properly.
The idea that society would use forced IUDs to stop women who are at serious risk of having damaged babies due to consistent taking of drugs or alcohol in high amounts, or hormones that will damage the foetus is not outrageous. I'm not saying I have the answer or that we should do it, but in an ideal world I would love no more pregnancies resulting in foreseeably damaged babies.
Conclusion - I almost support the tweet's overall message, but I would not tweet it, do not believe in forced sterilization and do not believe KJK tweeted it or supports forced sterilization.