A big table is hard to interpret. Here's histograms, including means, standard deviations and links to the CSV data that I took from their HTML table:
http://dose.se/~estan/installa...
In short:
PS4 games have a mean installation size of around 7.2 GB with a standard deviation of 11.1 GB, while Xbox games have a mean installation size of 10.5 GB with a standard deviation of 12.7 GB. The summary is misleading in saying that games "often" weigh in at over 40 GB. It's quite rare.
The link above breaks it down across "Major" and "Indie" games (division as at the article link). Short story there is: "Indie" games are on average tiny compared to the average across all games, while "Major" games are slightly larger.