Yep noted. Did some research. Boot process is completely different on the M1 machines to the Intel ones. The SSD has half of iSC and 1TR on it which is tied to the hardware. BUT it looks like you can still boot off an external disk in insecure mode and possibly use that to recover the system. I suspect the Linux dudes will come up with something in this space.
If the drive itself has a total, catastrophic failure then no. The macOS partition gets corrupted, sure can muddle around that . But if iSC ( iBoot preboot volume and Secure Enclave extended storage)and/or 1TR (one true recovery) is borked, it is bricked.
"...
As Howard notes in his article, Apple introduced the notion of the 1 True Recovery (1TR) partition with M1-based Macs. This additional partition, separate from a Big Sur startup volume group, holds the code and data that controls boot-time behavior. On Intel-based Macs, firmware serves this role.
One way 1TR differs from the firmware on Intel-based Macs is that the 1TR partition stores your decisions about startup security
policies, the directives you set in the Startup Security Utility available in recoveryOS. You can set a separate policy for each external volume you allow to boot your Mac, but that policy is stored
only on the internal drive in the 1TR partition. ..."
A little-noticed fact about M1-based Macs has started to get some attention. If the Mac’s internal drive is dead or fully erased, you can’t boot from an otherwise valid external drive. Why would Apple make that choice? Security, security, security.
tidbits.com
Minus hacking around at the iBoot level this doesn't have a 'work around by the Linux guys'. The policy of whether optional Linux bootloader is an option is stored on the Apple drive. iBoot doesn't talk to anything, but the Apple primary internal drive. (not surprising since iPhones/iPads/etc can only possible have one and only one internal drive.)
There is no "Internet Recovery" either. Can't boot to a minimalistic recovery system off the Internet from a minimized sized UEFI 'application'. The minimalistic down to smallest ROM possible is just the power/system management and secure enclave "OS" running shrunk down to just get the DFU process done. But that is about it. If the internal drive is 'lost' then the system just into a deeper , secure mode (not looser).
Apple has hyper integrated the security and boot subsystems here. They are extremely co-dependent.
I have three M1 macs here so not a problem but I can imagine people having to haul any bricked ones back to Apple or a third party to get this sorted.
In part, this "there is always a mac just around the corner" philosophy that probably works insanely great inside of Apple probably contributed to why Apple thinks this set up is a decent trade off. Even if the internal drive drops into a "failing so go read only" mode then still could external boot if had the policy set up in advance. But if the drive metadata is completely screwed up then can start over. And if the NAND chip(s) themselves are the root cause of problem then at least in Studio ( and perhaps some other desktops) replace and start over from scratch.
But for the soldered down NAND chip systems that logic board is done.