At around 20 mins, when you hide everything that's not selected it also hides the ends of the selection. Any ideas why?
I'm not 100% sure what you mean here..rewatching that part of the video still looks like everything is behaving as expected. Could you clarify what you mean by "also hides the ends of the selection"?
Nevermind, I was selecting the lid planks with loop selects instead of using L to select the mesh island