On a large site with more than 3600 users, the Security report shows "Found 2353 Users that must be trusted". This means that almost all users enrolled in any courses must be trusted.
The only override student role has is about viewing participant and user profile (set to prevent).
The only override Authenticated users has is about completing and entering feedback, set to Prohibit.
Looks like it is very dangerous to enroll students, beside the suggestion to verify trust of the very long list of 2353 users.