@pitaj That makes sense.
Thank you, I think that answers my question.
@andrei-lopatenco You are correct, there is no Flags API at the moment... there never was one for the Write API plugin, and when it got ported into core, we didn't make one either.
But it sounds like a good idea.
I am seeing similar behavior too for read API (for example get user by email api), master token and _uid are ignored when sending request. The document states that master token can be used, however it doesn't seem to be the case for all APIs.