Binaries are built on CI infra with logs that are publicly available and with all the source code doing the builds publicly available. Effectively the same process as local, from source builds. The bottle DSL ensures that the SHA binaries are not tampered with between when they were built (and the source code sha checked) and when they are delivered.

I know this is still a different trust model, but, IMO, not too different.

I know reproducible builds are on the radar for Homebrew in the future, and that should ease some of your concerns too.

For a good thread on Homebrew security checkout https://twitter.com/c_pellegrino/status/1093195802871246848