50 PRs with a thousand developers is definitely not healthy situation.
It means any developer merges their work very, very rarely (20 days = 4 weeks on average...) and that in my experience means either low productivity (they just produce little) or huge PRs that have lots of conflicts and are PITA to review.
It means any developer merges their work very, very rarely (20 days = 4 weeks on average...) and that in my experience means either low productivity (they just produce little) or huge PRs that have lots of conflicts and are PITA to review.