At this point I don't know if anyone at github does code reviews. They hide large diffs as you said, but navigation is also broken, I have to click several times on a filename for the UI to scroll to it.
They also decided that comments should not be visible instead you have to hunt for a tiny avatar of the person who left them. Very puzzling
Yeah, unlikely they use Github much internally.
At least they finally fixed the sidebar to use anchor tags instead of divs, so right-click can open the file in a new tab. It's still a bit wonky, since the a tag is only the size of the filename, with zero padding. It was broken since they introduced their new UI sometime last year.
Maybe by the end of 2027 clicking a filename actually takes you to it.