Thanks for that information, Tamara.
To be accurate, JKR raised concerns about allegedly " increasing numbers" of people detransitioning, rather than a high overall percentage.
And whilst JKR does mention detransitioning, her concerns may have been based more on her claim that "60-90% of gender dysphoric teens will grow out of their dysphoria."
I shall make some amendments to make my remarks more accurate.
Thanks for your help!