This would happen frequently at a previous job, and it bothered me. Thousands of lines of changes in a repo where you have very little context, not just about the change, but about the project as a whole. While you're trying to learn about the project, submitters are hounding you with Slacks to get the review in so they don't miss some arbitrary sprint deadline.

If code reviews are to be done seriously, time should be allocated / scheduled properly (for the reviewer.)