When I make a member an Administrator but do not add them to any additional user groups or grant any permissions, they can access the ACP (just caches and error log) but they also have access to the Moderator Toolbar so can see reported items and items in the moderation queue.
This is despite them not being a moderator or having any moderator capabilities.
That seems to contradict Mike's post here:
That's part of the "moderator toolbar", so it's only shown to people that are actually moderators. That's not changable at this time.