To cut straight to the point, it's not unusual, most grow out of it, and it's often a symptom of another psychological problem.
The news articles are in Dutch but Google will translate them for you. The paper itself is in English.
From the NOS news: https://nos.nl/l/2511984
News article from Groningen University Medical Center: https://nieuws.umcg.nl/w/twijfels-jongeren-gender-verdwijnen-vaak
The study: https://link.springer.com/article/10.1007/s10508-024-02817-5
I haven't had a chance to read it all yet but wanted to share!