Can I ask you what Guests has got to do with a custom role I created (fake-users)? Are you suggesting that any custom role is interpretated as Guests (read-only)?
You can find attached the Guests permissions as it is. But the problem is that non-logged in users are able to see profiles of members that are completely hidden (i.e. fake-users with no-access permission).
The usergroup who can see the user with custom usergroup is the Guest, you should disable Guest to see them to solve the problem. Please see the screenshot and disable the "Can view members" and "Can view profile":
Not loggin users are the guests, If you disable these options for guests nobody can see the users without login. The user whose permission is disabled can logout and see users as guests, so you should first prevent the guest permission then other permissions.
@robert thank you very much for the clarification and for the solution, which I confirm is working! 😛