Checking the first one

> Intel staging area for llvm.org contribution. Home for Intel LLVM-based projects.

Seems like they use it to contribute to upstream which is business as usual?

Three of those are forks to upstream back to the main repo, and one of them is dead.

You should have ordered them differently to not distract from your point: That most LLVM-based compilers do eventually need to write patches for it and usually ship them before upstreaming, they can't just use an existing release. I at least have always found that to be true to build such compilers from source.