It's not being noticed because you're rebasing every time.  It's OK to push new changes during the review.  The main purpose of rebase is to clean up your commit history before pushing so you don't end up pushing a bunch of 'WIP' and 'hope this fixes it' and 'attempt number 2' commits for merge consideration.  It is also useful if next has moved dramatically during your development.

It's fine to use rebase when you need to but you probably don't want to use it every time you push new changes.  Github will be better able to keep up during the review.