The other day I noticed that some major apps like Instagram, Snapchat, Nike, Facebook, etc. can have multiple updates (sometimes three or more) in only a few days (less than three or four). See this screenshot from Instagram's update schedule below and notice that they've published three updates in the past four days.
How is this possible? Apple takes at least a week or more per app review (including minor updates). In order to speed up the process to say two or three days, one can submit an Expedited App Review Request. However, Apple only grant these on a limited basis.
How do apps like this get updated so darn quick? Is Apple playing favorites to major companies and keeping smaller developers at the bottom of their queue?