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.
Oh interesting I didn't realize the role of adjectives has changed recently. So war and my nuclear war mean the opposite things now. I'll keep that in mind.