Of course Apple advertise running your own kernel code on these machines. Here's the official documentation on custom kernel extensions (which are functionally equivalent to allowing other OSes):

https://developer.apple.com/documentation/apple-silicon/inst...

And here's the kmutil manpage that explicitly describes the option they added to support fully custom kernels, which is what we use:

https://keith.github.io/xcode-man-pages/kmutil.8.html

And here's a blog by the head of XNU development at Apple explaining how to build and run your own XNU kernel for these machines:

https://kernelshaman.blogspot.com/2021/02/building-xnu-for-m...

This isn't an accident. This is a documented, explicitly advertised feature that Apple put a significant amount of engineering time into developing.