This is amazing work, and I certainly respect the talent of those involved.

That said, my question to those interested is why? I've been a daily user of both Ubuntu since 2005 and Mac since 2012. There are some edge case differences but for the most part they are so similar that I nearly always run the same code on both without modification. Clearly I'm missing something important but I'm curious what it is. Thanks in advance.

One reason is for continued software support after Apple drops macOS compatibility for your machine. Intel Macs could be patched to run newer, unsupported OS versions (essentially hackintoshing your real Mac) but from my understanding that's basically impossible for Apple Silicon Macs.