It isn't very clear on that, but I think it is a way of automatically downloading binaries from Github releases. If so, that wouuld work well in some cases, and poorly in others
There are always tradeoffs with any packaging system, no matter how transparent/simple.
" Unless $HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK is set, brew upgrade or brew reinstall will be run for outdated dependents and dependents with broken linkage, respectively.
Unless $HOMEBREW_NO_INSTALL_CLEANUP is set, brew cleanup will then be
run for the upgraded formulae or, every 30 days, for all formulae."
Really annoying defaults considering brew is a developer facing program not a consumer facing program where the tradeoff between security and functionality makes more sense.
This is why I still reach for conda whenever possible. I am at least prompted before 100 things are installed.
It’s been many years since I’ve had a problem caused by Homebrew’s design but if you like keeping things frozen like that, it sounds like you might be a better fit for Nix or working in containers where you aren’t fighting a distribution designed to stay consistently current across the entire system.
It isn't just that things "work together" but in some cases authors change how their tools work between versions and I may have stuff installed that depends on these outdated paradigms. In other words, the stuff I have built is not sure to work together with updated brew packages. I have a few scripts for example where numpy complains how I call some function will no longer merely throw a warning but actually not work at all in future versions. I can either spend my free time to rewrite the script to do it how the numpy authors now want me to do it, or I can just not do that and live on the old numpy and not be any worse for wear.