>Where does it stop?

I don't know but macOS is making it ever more difficult to manage storage, with lots of random things under "macOS" pushing ~40GB or "System Data" that gets a crapload of unrelated things like podcast [1] downloads, with no easy way to purge.

[1] I spent too much time hunting down ~250GB of missing disk space, and it turns out it was the Podcasts app's cache, while the app itself reported no downloads. I fully expected this to be managed automatically, but was getting out of disk space warnings. It's a mess.