That's for non-public add-ons. If you submit a public add-on, even a minor update, it has to go through the AMO bureaucracy. I currently have an update that was uploaded on July 10, 2015, and is at queue position of 64 of 137. There are no code changes; it's just being updated because Mozilla changed their build system.
This seems to be part of Mozilla's effort to be more like the Apple and Google stores.
Mozila AMO - Learn to embrace the pain.