Gotta love that Github has decided that hiding largest diffs by default was a good idea. It's not like the amount of changes has any correlation to importance, right? And to top off the joke that they are, it's still amazingly slow, even when you skip the bulk of the code.
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