I would argue if not using the OS python is the correct way to do things then python by default should not install at an OS level. Installing in the OS should be left to the OS only and the default should be that python installs per project which special instructions for installing it as a default for a user and special special instructions for how to replace the OS level one.

I really wish this was the default for all languages but the majority default to "install in your system" and then I run into the problems you and the OP mention.

As it is, finding out/figuring out how to work around the default is always magic incantations and spells buried on page 947 of appendix G if you're lucky or else spewed around the internet in drips and drabs by unreliable and or outdated sources.

As an example I wanted to contribute to some conformance tests for some browser API. The test suite used selenium which uses python all of which wanted global installs. I tried for a few hours to get it to run with local installs but I failed to find the correct secret ritual to perform and after a few hours decided I no longer felt like searching for the correct oracle to enlighten me.

ps: For my particular needs a VM was not a solution