Microsoft's kernel is also famously behind the times because they can't update key parts because of the stable API. Like how the scheduler only knows about banks of 64 cores at a time, and you have to manually load balance your threads from user space in some cases. Or how they couldn't change their VFS to compete with Linux's expectations because they reversed the caching model. The NT filesystem cache sits between user space and the filesystem so internal metadata isn't cached by default but instead needs manual work from each day driver that's always not quite implemented well in practice. On Linux the cache conceptually sits between the FS and the block device so metadata is actually cached 'for free'. Because of these problems it was faster to literally run a whole other kernel for WSL2 rather than the apples to apples of WSL1.