Nope - git is mostly fast on Windows. It's magit that's the problem - or rather how magit does things. It launches several git processes to do basic things like status or commit, and that is fundamentally slow in Windows.
So you are saying git is slow on Windows, but only because starting any process is slow on Windows. Interesting. I've heard there is work in progress to have magit use libgit2 instead of running the git executable. That should help.
See https://magit.vc/manual/magit/Microsoft-Windows-Performance....