I could be wrong but I think a lot of the M1 support being added to linux is around what used to be called the "chipset" of the system and not the CPU itself, which is running a typical ARM64 ISA.

Getting the device tree set up, initializing graphics and all the peripherals, and the boot process is where Ashai Linux has done the vast majority of their work.

The M1 does have its own co-processors that I do not expect to ever get support, such as AMX.