The Drupal core update mechanism does not verify the major version of the database. Drupal Core 9 will execute updates on a Drupal 10 database.
Download and install Drupal Core 10.0.3 (minimal). Swap core, vendor and root files with those of Drupal 9.5.4. Run update.php.
There will be no warnings or errors.
Drupal update.php should verify the major core version of the database it's making changes to.
Active
9.5
Last updated
That is because update hooks are numbered sequentially. But, by convention update hooks must begin with numbers befitting the target major version.
The steps to reproduce describe a process that is not supported.