I suspect for their public facing products (i.e., the claude ecosystem, which is like four products), the review process is much more rigorous, and the PRs merged in per day is likely much much lower.

A few things about their post: they're doing trunk development on a mono-repo. With their tool, Antique, instead of having branches, they just merge in stacks of commits, which they call "Change Requests". I have to wonder if their engineers have the models running and don't even realize the models are putting up a change request and if that's contributing to the high number.

Additionally, I would guess that a lot of the code merged into that mono repo is for experimental projects or other internal tooling that is in prototyping stage.