How to allow admins "web"-access to all resource groups?

I have several user groups and several resource groups. In the manager, the admin user group can see and edit all resources, regardless of their resource group. However, in the frontend ("web" context), the admin users can only see those resources, when I explicitely assign the respective resource group to the admin user group.

In my understanding, when I do not assign a specific resource group for the admins, they should be able to see every resource in the web context, just like they can do in manager context.

Is this Bug, Feature or my deep misunderstanding of the ACL system?