I have developed a habit of going through my own pull requests immediately after opening them, and adding a "don't forget this file" comment to all the ones that get collapsed.
'Cuz yeah, I've seen some nasty stuff sail past code review simply because it's so easy to accientally miss those files.
Good one, I'm going to do that too, thanks. It's pretty nuts how broken a UI is that it forces us to do stuff like this though.
I feel like everything about the GitHub PR UI is targeted at reducing the code review job to being a human style checker. Minimal context, no code navigation, abysmal rename following.. it's really hard to review the design of a change.
The reason for the automatic collapse is due to performance. Also it's not uncommon (depending on the language and framework you are using) for the biggest files to be just a mere dependency lock file kind-of update.
'Cuz yeah, I've seen some nasty stuff sail past code review simply because it's so easy to accientally miss those files.