In principle I would agree, but the world isn't black and white. First of all, in the PC world, there are few machines which are completely and well documented. That Linux runs on so much PC hardware is more due to the popularity than great documentation. NVidia just recently finally open sourced their drivers.

Could Apple improve the documentation a lot? For sure! Bu on the other side, the ARM Macs are a very nice platform, so I can understand the desire to use it. There is no competition at the moment, so it would be wrong too, to not support Linux there.