>> This is a company that actively fights right to repair and implements software DRM to lock out non-Apple authorised replacements.
But they do all these things for obvious reasons. Reasons you and I may not agree with or be happy about, but still obvious reasons. In the case of repair/replacement it's just because they want you to use expensive replacement parts, they want to lure you into their Apple stores, and they don't want any liability/accountability for repairs with 'unofficial' parts.
I don't see how providing specifications about how their GPU's work so someone can make a Linux driver out of it hurts their commercial interests or liability though. Yes people may screw up their system if they install Linux on a Mac and it doesn't boot anymore, but as long as you can still take it into an Apple store and they can restore it to MacOS, why would Apple actively fight the extremely small minority of people who want to do that? And even if more people (developers/enthusiasts) would buy M1 hardware and immediately slap Linux on it, why would they care about that? They still made the sale, and these people will still walk around with a machine with a big fat Apple logo on it?
They previously spent a lot of effort accomodating people who wanted to run Windows on Macs using Boot Camp, so why would they be worried about people running Linux on M1 macs?
Edit: I can imagine Apple want to protect their IP and hence don't want to disclose anything about out it, period. Much like NVidia and most other GPU manufacturers do. But if AMD and Intel can be OSS-friendly, Apple could be too, apparently IP protection does not have to be a deal-breaker.
Don't hold your breath. Apple's stance by actions is the opposite.