It seems like you are mixing up the “ecosystem” with the application: desktop, mobile phone, etc.

10 years ago there were mobile phones running Intel Atom and they were just as bootlocked as any other phone. I personally have two intel based chromebooks and unlocking their bootloader requires taking them apart.

Whereas my arm based Pinebook Pro requires no unlock at all. I have lots of Arm based SBCs and all of them came unlocked as well.