> doesn't have time to review the full diffs they're upgrading to.

Again, why are people expecting that you need to review the entire thing? You don't have to, you have to look at the download source (a github organization or a domain name or a cdn bucket) and look at what dependencies/other junk it pulls in. Usually this is 3-5 lines at max, and usually only the binary/source is taken from github/server, the rest is from official Arch repositories.

Of course it's unrealistic to expect users to review 100% of the code they run on their machine, that's why no one is expecting this, nor claiming that users should do this. But reviewing 3-5 lines when installing software from literal strangers on the internet, isn't so much to ask.