Permission in Rest Api

Hello Xwiki Community,
Can someone please explain the permissions assignment exactly it doesn’t happen what I would expect.

My situation:
I have a main page,
User A has the permission to view and edit the page and all bottom pages.
User B has the permission to view only

Now I create a subpage
User A does not get additional permissions
User B gets additional permissions to edit the page.

My observation:
I query via the Rest api with user A the available Spaces.
/xwiki/rest/wikis/xwiki/spaces

Here the corresponding subpages are also shown to me, as long as no additional permissions are given for them.

As soon as I set the rights for user B, I can’t find the corresponding Spaces with user A.
If I additionally give user A the right to view, I see the spaces again.

My expectation
Because user A doesn’t get extra rights in the subpage, the rights of the main page are valid, here he has the right to view and edit this page and subpages.
This does not happen, where I my thinking error?