Okay, I followed the "view on YouTube" link for that video, and apparently several commenters there are also puzzled about what version was being used (I don't know French, but Google Translate gave me enough of the gist). I checked the dates, and I'm fairly sure that can't really be a 1.7.10 version of Ancient Warfare 2 - the video was published Mar 20, 2014, but the oldest 1.7.10 build of Ancient Warfare 2 on GitHub was released Jul 13, 2014. Even the 1.7.2 builds only go back to June 2014, so more likely the video publisher was actually playing in MC 1.6.4.
The catapults/trebuchets are probably part of the "vehicle module" that is listed as "WIP - Will be included at a future date." I found a GitHub issue where somebody requested them to be added to the 1.7.10 version, but it was closed without explanation.