It's probably pertinent to mention that the Python installation ecosystem is a hot mess, with multiple ways of installing Python (e.g. standard Python installer, multiple different packages managers on different OSes, Conda, and myriad package managers which can also install Python. And of course, these can all be in different locations, and may have different approaches to installing libraries.
Which is to say, I don't blame the author for wanting a single installation that his app can manage and rely on, even though I wish it was different.
The app is vibecoded. The author isn't making decisions about these tradeoffs and possibly wasn't aware of the implications of these decisions at all. The robot they used tried to fulfill its given prompts at the expense of everything else, which is why it's looking in bad directories and trying to install Docker environments in the build script.
I suspect that some of the author's comments in this thread are vibe-written, also. They are LLM-flavored and contrast strongly vs. their regular commenting.
It's not open source if it has to download binaries from the internet to run.
I agree with the sentiment but that definition would make open source Windows programs not open source either.