Barozi said:

wasn't there that one update that adds 5 hours of additional content ?

But overall I guess you're just a fast player like me. For every game that is on HowLongToBeat.com I'm faster than the average, quite a few times even among the fastest runs without even trying.

It's not about additional content, it's about the main storyline. People called Ground Zeroes a 2 hour game, even though the game had side missions.