Earlier quoted context omitted.
That's nothing you can't already do with VMs, and avoiding vendor lock-in.
Actually it is different. The difference might not matter in some cases, and in other cases it will. Running on a VM means running on emulated devices, running in a Userland host means running on native devices. WSL is to windows as Wine is to Linux. A really trivial example is the buffer cache. On a Linux kernel it will take big chunks of memory to buffer disk blocks that it has read and dirtied. When run in a VM it…
A compatabilty layer generally takes away the kernel's role. Is that the case here?