There is more to reverse engineer on the M1 than there is on a random Intel based mac. Intel has been a reasonably good opensource steward as evidenced by all the .intel.com contributors to the linux kernel, and a goodly amount of documentation. Yes the intel has plenty of closed source firmware/etc but a lot of it exists to provide standardized boot flow/etc.
The M1 has none of that, so a random intel mac's reverse engineering is limited to only the parts Apple changed from what is mostly a set of platform standards that have been built up over decades. The core system IP (interrupts, iommu, virtualization, pci, memory controllers, USB, etc) already have linux drivers. The M1 OTOH isn't even fully compliant with the ARM instruction sets because they apparently have extended even that.
So, yes the hardware may not technically be locked down, but for all intents it might as well be, since Apple could have picked up the ARM system specifications and conformed to them but they didn't. The whole thing is vaguely reminiscent of SGI's failed attempt to create a new "PC" standard by dumping all the legacy, designing their own chipset/etc and running their own firmware. Yes it was an x86, but it didn't run anything except their blessed version of windows NT (IIRC). It was a dead end, because it turned out it didn't really offer any advantages, over a boring old PC, cost twice as much and removed the ability to run a bunch of software.
The M1 is much the same, it loses out in a lot of ways not only on the software front, but the hardware front as well. If it weren't for its fairly outrageous single threaded perf, which is at least partially enabled by being fully two process generations ahead of intel it wouldn't be noteworthy at all.
The M1 has none of that, so a random intel mac's reverse engineering is limited to only the parts Apple changed from what is mostly a set of platform standards that have been built up over decades. The core system IP (interrupts, iommu, virtualization, pci, memory controllers, USB, etc) already have linux drivers. The M1 OTOH isn't even fully compliant with the ARM instruction sets because they apparently have extended even that.
So, yes the hardware may not technically be locked down, but for all intents it might as well be, since Apple could have picked up the ARM system specifications and conformed to them but they didn't. The whole thing is vaguely reminiscent of SGI's failed attempt to create a new "PC" standard by dumping all the legacy, designing their own chipset/etc and running their own firmware. Yes it was an x86, but it didn't run anything except their blessed version of windows NT (IIRC). It was a dead end, because it turned out it didn't really offer any advantages, over a boring old PC, cost twice as much and removed the ability to run a bunch of software.
The M1 is much the same, it loses out in a lot of ways not only on the software front, but the hardware front as well. If it weren't for its fairly outrageous single threaded perf, which is at least partially enabled by being fully two process generations ahead of intel it wouldn't be noteworthy at all.