There are some API endpoints that, when developed, were classified as internal and not publicly documented. You are probably running into some of that. I’m not a fan of this. At least on SonarQube Server, a fearless user can tick a box to see those internal APIs in the docs. Not so for SonarQube Cloud today.
It might be interesting to understand that for several years, the teams working on SonarQube Server and SonarQube Cloud (nee SonarCloud) were largely separate teams at Sonar. That is no longer the case, but there’s 5 years of somewhat diverging products (and different implementations of features) to reckon with. Ideally we will eventually land on more consistent behavior and a common(ish) v2 API between the products. That will take some time.
In any case, you can always snoop those internal APIs as you’d expect.