In what instances should a bottom navigation be hidden (mobile app)?

Many mobile apps have bottom navigation (think Instagram, Twitter, etc.). However, for some of the pages / processes, the bottom navigation disappears.

E.g. On Instagram, once you do the process of uploading a photo, the bottom navigation disappears and just shows the entire process from start to finish. The bottom navigation shows up again when you've completed the uploading.

So is it alright to assume that when you do the main goal / action for the app, the bottom navigation can be hidden to make the user complete the process without any distractions? Also, in what other instances should the navigation be hidden?