IOS, user is enabled to remove remote management

Dear Sophos,

All devices ios 13.6, Apple DEP, all the same enrollment procedure.

In Setup. Apple Setup, Apple DEP profile 'user can remove MDM policy' and 'skip policy assignment' are both unchecked

I noticed that a user is able to remove remote management from their ios-device.

I noticed this after enrollment of an ipad 2019 and iphone 11.

However, i also enrolled an iphone 6s, resulted in not having the possibility of removing remote management.(?)

What to do to make sure that users are not able to remove remote management.

Any ideas?

Best regards,

Roelant Bakker.