UUIDs are not ignored when uuid: null

Problem/Motivation

This installs fine but doesn't seem to make any difference to whether uuid's are ignored on my installation of Drupal 9.5.10 (currently the latest build)... EDIT, ok, it works when a valid uuid is present, it doesn't work when uuid is null.

Steps to reproduce

1. Install Drupal 9.5.10 (in my case I have other modules installed but nothing I can see which would clash with this)
2. Install module
3. Enable module
4. Copy paste suggested ignore patterns from the Readme (removing leading spaces)
5. drush cex
6. change uuid to null in a config file which should match the aforementioned patterns
7. drush cim --diff
8. the changed file shows up as a changed config, hence uuid has not been ignored

I've also tried using the exact filename (no wildcards), using a single entry, using drush and the web interface, nothing seems to work for me.

(Edited)