This is a question of the artifacts distributed as part of Arch Linux, the tar.xz packages. The idea is to be able to reproducibly build a package from source (where "source", yes, may include binary assets and blobs), and check that the copy you built matches what Arch distributes, byte for byte. This way, you know the packager hasn't introduced unexpected changes.

Since end users build AUR packages themselves, there is nothing distributed, and nothing to verify.

You're describing what those AUR builds do not what they are.

Reproducible builds are for artifacts that are... built. Plenty of AUR recipes download blobs and explode them, but the resulting xz package isn't actually hosted in the AUR.

A tool like rebuilderd would only be relevant to the AUR in the case that somebody is publishing generated AUR packages to a repo for others to install without building them directly, and then you'd like to verify those.

I think of the AUR packages as more like ebuilds with fewer safety catches 8)

proprietary drivers from nvidia are provided by the Arch mainline (core) though?

right you are, i've been on beta for years and had forgotten.

point still stands, aur does distribute executables once in awhile.

> aur does distribute executables once in awhile.

The AUR doesn't distribute those executables; it distributes the instructions for the user (or some software working on behalf of the user) to go fetch the executables themselves. This is an important distinction, because the official Arch repositories _do_ distribute executables, directly to the user.