One issue I see with including something like Pi is that it's intentionally bare bones. I don't think anyone uses Pi without some basic custom extensions (subagents, check lists, etc), so this benchmark may not be representative of a realistic setup.
Would be interesting to see some sort of ablation test too. E.g. what parts of Codex contribute most to the perf, and can they be recreated more minimally in something like Pi.
It does seem a bit odd to say "We tested all of these bicycles with the same rider" when one of the test cases is actually a bare high-end frame with no components on it.
It's even weirder given that another of the test cases is essentially "We put parts on the frame (OhMyPi) and it went faster!"
I think it's still a useful data point. For example, omp, which is pi with some default extensions, scores worse. I do agree that adding more configurations of Pi would help though.
I use Pi barebones.