If you change platform keys, it looks to me like you can brick your system if hardware component drivers that execute during boot are signed by microsoft keys.

Microsoft will make sure many of their partners sign hardware drivers with their keys to be windows 11 certified of course. No other reason.

They will encourage manufacturers to only allow secure boot in UEFI. Then at some point they will stop signing UEFI loaders, like shim, that linux distros rely on to boot.