Advanced Permissions for Page Owner somehow not going well

Permalink
Hello Community,

I am running into a issue I do not understand well.

I set up a Site (5.6.3.1) where Users can add Pages through Composer by specific page type.

Now I'd like these user to be able to edit the content of these pages afterwards.

I set the page types' permissions to "Edit Contents -> Page Owner" and "Approve Changes -> Page Owner".

But when I login as a TestUser and check one of the pages created, I cannot edit the contents, but could add a SubPage, even though I forbid this in permissions.

Is there something unlogical with permissions or am I missing something about how to do that?

Please help :)