Cachy has, at least in my experience with a Zen 5 processor, it's own special Arch pacman repo with meta packages for various processor types. I believe for the most part mine uses Zen 4 packages.

Add your processor meta package and it adds the appropriate repo where packages have been custom built with feature flags / optimizations for that specific architecture of processors.

So it's a little closer to Gentoo or LFS in those regards, without you having to actually build every package from scratch.

So while yes any distro could do this, in practice a lot don't bother and only release basic i686/amd64/arm32/arm64 sets of packages. Whereas Cachy offers zen4-amd64 packages as an example, and I assume they offer various Intel architecture and other AMD architecture specific packages as well.