The setting for that is in the tesla app, and it works with gen 2 tesla wall connectors (which are not wifi enabled or otherwise connected to any network) so it should be controlling the car, not the evse.
I cant test it because I have a gen 2 wall connector, but can confirm the setting to set a percentage allowed to charge is in the tesla app, not anywhere in either the car, or anything the gen 2 wall connector currently does.