- Time to install packages - Versions of things - Has the compilation (when required) failed? What dependency versions are installed? - CPU architecture - OS version ...
There's a lot more that can be sent from the client that's not available on the server side.
> I fundamentally don't 'get' what richness they actually need.
That's fine. Perhaps you could ask them instead of ranting about what you don't know or don't 'get' in a public forum?
> to know their software works for their users
Sounds like you're not very far from understanding why they want better telemetry.
> Prior to release (...) and you know anything less will work too.
Things break in unexpected ways. OSs are complex systems and there's a lot of interactions between components. Homebrew's user base is enormous and very diverse. There's 2 different architectures, many OS versions, lots of environment variables that might be set differently in each user's systems, different versions of libraries, ... I could go on but I think you get the picture.
If anything they need money, of course, and to know their software works for their users. Prior to release have a test system install the full base, test those packages work, and you know anything less will work too.