Last time I checked x86 is not open, it’s licensed just like the lightning cable, och and USB-C.
ARM and phone manufacturing is a hot mess in comparison. We're still trying to reverse engineer M series MacBooks and iPhones are off limits. Android is also not open source, no AOSP does not count.
There would be a lot more competition in the space if the hardware had proper specs, like x86 does.
It’s great that documentation exists, but it doesn’t make for competition. ARM is at least licensing out to more than two manufacturers.