It's still ok even without systemd. Technically systemd is disabled by default, you have to turn it on with systemd=true in /etc/wsl.conf.

I can't find a definitive source with an open ticket but if you Google around for "WSL 2 systemd delay startup" you'll find assorted folks talking it about with a number of different reasons.

I just went by my end results of there is a delay with systemd enabled and no delay with it disabled.