That doesn't make sense. Why would llama.cpp need to move any faster than ollama? For that matter, why not have a llama.cpp package and llama.cpp-git in the AUR?
The claim was that llama.cpp moves too fast to be in Arch's normal repos. But Arch does package ollama. Therefore, either 1. ollama somehow avoids the need to move fast, or 2. it moves at an acceptable pace when packaged.
Edit: Or perhaps put differently: If ollama includes a copy of llama.cpp and has a non-AUR package, why can't there be a non-AUR package that's just llama.cpp without ollama?
Sometimes Arch has the software you want at the version you want, other times it doesn't but other distros do. That's why there's half a billion distros instead of just one.