Then other factors like games bought but not played or played offline. Or bought for Christmas presents.
Well it depends on how Playstation handles it. Games bought digitally but not played could still count (there are hints that it does on Xbox). Physically though that's not possible.
Christmas presents.... maybe. Some of the data was compiled even before Black Friday. It's definitely not comparable for new releases at that time.
Playing offline still counts if you go online at any time after that. So only consoles that have never been connected to the internet wouldn't be counted.