Even with a small, self selecting study those numbers are so bad it's hard to argue there isn't a problem going on.
What percentage of 18 - 30 year old women generally experience incontinence?
Looking around the internet the most unfavorable numbers I could possibly find put it at '20% of young women'.
The gap here is just so large between the 'control' and the study group, you have to seriously ask why. Being self selecting doesn't resolve the question here.
If this is anywhere near accurate then there no way that doctors who treat trans identifying females regularly don't know there's a problem.
Now ask yourself why did those NHS adult clinics without data from Hilary Cass when asked for it.
This would very much explain why they refused to cooperate.
Can you imagine the advertising on this:
"Transman incontinence pants, specially designed with your unique body in mind. (Have the nappy shot with different shaped pants and the ubiquitous water coloured water here). Helping you be your true authentic self. Now you too can go about your day, not worrying about unpleasant odours. You too can now go carefree like Cismen.' (we have have some skating imagery going on here too)."