There is a lockdown as you cannot even boot linux anymore...
I don't care that I can't run Linux on my Mac. If I wanted to run Linux, I'd have different hardware.
Of course, Apple as an OEM does not support running non-Mac OSes, so virtualization should still be preferred for most use cases.
They had crappy code signing policies (only store apps on Windows RT tablet) which guaranteed poor adoption but that was a policy decision, not a technical one.