Technical measures are impossible in this particular case.
However, I would say that the complete lack of benefits or incentives makes it very unlikely.
Doing so could be illegal and collecting data which is otherwise useless is only a liability and a waste of resources.
Basically the admin own self-interest I would say is what's stopping them. That said, if someone is individually afraid due to a bad relationship with an admin, then personal motives could void the above, in which case, they should change instance probably or use a VPN at least.