I believe it's at least partially due to Windows Defender, but creating files in WSL is dog slow.

  $ mkdir scratch;cd scratch;time perl -e 'for (1...10000) {open(F,">$_");close F}'

Runs for 5 seconds in WSL, 100ms or less on an actual Linux box. I do like WSL, but this sort of thing limits how useful it is. Pull some big repo with git, and Zzzzz.