> The ideal PR size is 50 lines because that’s the median size on Github.

???

No, that's not why it's arguing that it's the ideal size. Where did you get that idea? (TBH I doubt it's the case - apparently the average PR size on GH is nearly 1000 lines [0])

It's arguing that it's the ideal size because (1) PRs of that size end up getting reviewed and merged the fastest; (2) PRs of that size end up getting reverted the least, implying that they're less likely to cause breakage; (3) PRs of that size end up getting more review comments, implying higher engagement and less rubber-stamping (there's a concern that this could imply unnecessary bikeshedding that slows things down, but see 1); and (4) PRs of that size end up creating the highest total throughput.

I suppose that doesn't "prove" anything, because correlation doesn't imply causation. But it gestures towards it.

[0] https://www.keypup.io/product/average-pull-request-size-metr...