1. It was a major update Google would not like to make open
B. It was one standard update among many others
C. There was nothing and few websites were influenced as a feature of the standard intermittent update
Google has however denied any such overhaul occurring and emphasized that several updates continue happening at Google.
The Quality Update had happened in May this year and it was affirmed by Google that it was a core ranking algorithm update. Truth be told, it was alluded to as "Phantom 2" by the business circles; since it was felt that it was similar to a continuation of the first Phantom update in 2013, which was later named as Phantom or Phantom 1.