A super fast one. After one click, within 2-3 seconds I can have an Ubuntu terminal open with wsl. To spin up a vm from let’s say VMware, I need at least 10times that.

I don't think that's magic in the hypervisor, so I doubt it affects overall performance of the VM very much. But WSL images have a special boot process instead of a full init system like systemd, which is probably where the fast startup comes from. Maybe it also has to do with how they configure storage for the VM. On real hardware with a decent SSD, Ubuntu usually gets you a graphical login in less than 10 seconds.

Anyway it's a cool feature, and I'd love to know more about how it works.

And the fact that they probably use a slimmed down kernel with just the right amount of modules, I guess.

In any case, booting Linux (the kernel) is always incredibly fast, and booting to a tty, without all the systemd units that are generally loaded, is incredibly fast per se.