Rewrites are a different beast, I doubt they are fairly comparable. They probably have realized some better abstractions now that eases implementation, and may thus also boost performance. Also, Go’s gc has never been considered “good”. OCaml also just recently got multitask support, didn’t it?

Nonstandard lifetimes are not really helped with arena allocators though, and not everything is needed in each phase, or is there that divided phases at all. But you may be right, I honestly can’t tell with certainty.