For what it's worth, here's a patch for git-el to have the directory created, after Agustin's suggestion.
diff -Naur git-2.30.2/debian/git-el.dirs git_2.30.2-1.1/debian/git-el.dirs --- git-2.30.2/debian/git-el.dirs 1970-01-01 01:00:00.000000000 +0100 +++ git_2.30.2-1.1/debian/git-el.dirs 2021-05-22 23:52:16.409330369 +0200 @@ -0,0 +1 @@ +usr/share/emacs/site-lisp
