These are business machines. No company with centrally managed machines is going to allow the purchase of a laptop that allows a user to boot into a Linux live USB and work on the windows registry as data. End users' machines must be able to block 3rd party certs. It seems to me like having a simple BIOS option allows non managed hardware to boot anything the user wishes, while stopping non-Windows boots via a BIOS control with a BIOS password.