Do you honestly think Apple is going to keep this true for Macs in 2 years? 5 years? 10 years? I think there is slim to none chance that they give a shit about the "openness"of Mac.
As far as I'm concerned, Mac openness is just a cat that got out of the bag, before anyone knew they could produce a _mint_ from rent seeking walled garden platforms. I find it highly unlikely Apple is not looking to correct this mistake on Mac, even if it's done so gradually that by the time the pull the trigger, no one even bats an eye.