You absolutely can run docker on the CLI in WSL2. The only requirement is you have systemd running in your WSL distro, which is fully supported.
But again, they're talking about Windows, not Linux-in-Windows or virtualized Linux on Windows. Just because you can do something in WSL2 doesn't mean you "can do it on Windows", as much as you "can run systemd and Wayland on Windows" because you could run it inside a Linux VM...
WSL1 yes, but not WSL2, which the parent explicitly mentioned. WSL2 is just virtualization with a fancier name, might as well use VirtualBox and similar at that point.