lololol so I think I found a "legitimate" reason to install pipx with itself
I installed pyenv and then installed pipx with one of the non-system Python versions, but then I set the local pyenv versions in a directory to exclude the one pipx was installed with, thus causing any invocation of pipx in that directory to trigger pyenv's usual warning about the command not existing in any of the enabled Python versions. Turns out pipx install pipx makes it magically work again 🎉
(this is probably where I should put a disclaimer "don't try this at home")
