I followed your setup on a vanilla D9 and can report on the following:
Pathauto aliases are created as expected
but only for translated users
That is an expected outcome looking at Pathauto's code, since it will start generating language specific aliases based on a pattern only for the translated languages of each entity during bulk updates and only for ...
As mentioned in the comments, Always start with English string and translate that even if it's a one language only website, to ease the pain here's what I always do to keep the strings and translations contained to the theme itself:
open your THEMENAME.info.yml file and add the following:
'interface translation project': THEMENAME
'interface translation ...
It is indeed best practice to have the strings in your code being written in English (I will not discuss that point).
Yet, I had a similar issue once with a website (Drupal 7) a colleague of mine developed. The customer initially wanted to have the website in NL and FR and only many years later decided to add an EN version.
Problem: Strings in the code were ...