My understanding has been that the system-level Python is for your Mac’s system and not you. It’s covered in here, even though that wasn’t the main point of that post (here is counter vote for homebrew from mid-223). Plus, see and here and here. They even tried to make it more inaccessible in the last few years. However, maybe that isn’t what you mean and I’m misunderstanding what you mean there?
I know you’ve said you’ve researched this a lot, but did you also see here. And here from 2023.