The PC has always been an open platform. Documentation is readily available and the intention is for users to run whatever they want on the hardware. Completely different.

Intel and Microsoft control Secure Boot. If Linux hadn't already been so popular on servers when SB came about, it's very possible that PC platform would today be locked down to run MS-only operating systems.

Right, but that happened 10 years after Linus started writing his OS. If Microsoft had had their way then the PC would have also been a closed platform. This doesn't contradict my point in any way.

It doesn't change the way things stand today but still I think there's a marked difference between openness as a commitment and openness by lucky alignment of interests so far.