Confused about what kinds of users advcache works for

The documentation states :

The main beneficiary from these caching strategies will be authenticated users who have only one role

node_cache.patch: Caches built nodes for authenticated users with exactly one role.

Who is an authenticated user with only/exactly one role? Is it someone with no roles besides authenticated_user (so, no roles are checked on their edit profile page) or a person with only one box checked?

Looking at node_cache.patch and the advcache_array2int function, it looks like advcache is caching nodes for users with any combo of roles. Certainly *most* users have only one role, and the cache will help their activities the most. But is it true that nodes won't be cached for users with 3 or 4 roles? Either I'm missing something or the documentation is out of date

Thanks!