Disable auto-upgrading shared libraries

I am trying to update a Pipx install that has to stay on Python 3.8. Given 3.8 is end of life, pip has dropped support for it and has introduced code that requires >Python 3.9. That means when I try to upgrade this install, I get errors from pip (specifically TypeError: 'ABCMeta' object is not subscriptable).

I have tried forcing the shared library version of pip back to a version that supports Python 3.8 per the docs:

pipx upgrade-shared --pip-args 'pip<25'

However, when I run install or upgrade, the shared libraries are always immediately upgraded before running the pip install, producing the same error.

The docs mention something about how this should pin the pip version 'temporarily, until the next automatic upgrade, if that is not explicitly turned off'.

How do I explicity turn off automatic upgrades?