I can confirm that running autoreconf with Christian's version doesn't change the git tree:
❯ docker run -v`pwd`:/src tiran/cpython_autoconf
Rebuilding configure script
autoreconf: Entering directory `.'
autoreconf: configure.ac: not using Gettext
autoreconf: running: aclocal --force
autoreconf: configure.ac: tracing
autoreconf: configure.ac: not using Libtool
autoreconf: running: /usr/bin/autoconf --force
autoreconf: running: /usr/bin/autoheader --force
autoreconf: configure.ac: not using Automake
autoreconf: Leaving directory `.'
Done
3.10 on 3.10 [$] pyenv 3.9.1 took 6s
❯ git status
On branch 3.10
Your branch is up to date with 'upstream/3.10'.
nothing to commit, working tree clean |