My dear god, is this the first game you see the first gameplay reveal for a game? Because it would seem so. You can't possibly be serious in expecting to see everything a game has to offer in 1,5-2 minutes of video? Most of which is take by (in-game) cinematics?
It is EXTREMELY common that the first gameplay reveal is a very short, superficial look at the game. Last of Us showed a short fight against humans. It had nothing about a lot of the stuff that we'd end up confronting in the game, including showing zero stuff about the infected, or the horse-ridinig, or the puzzle-solving, or the hunting, or the story. FFXV's cinematic E3 2013 trailer focused on the cinematic battle against the gigantic Leviathan that had been summoned in the middle of a huge city, the combat trailer mostly showed combat in the initial city. There were none of the vehicles that you can presumably ride, none of the fields outside of the city, no non-combat exploration of the cities, no airships, no chocobos, even though based on past previews all of those should be in the game. Early trailers simply don't usually show much of a game. It's only when the game is actually nearing completion that more will be shown. Of course exceptions exist.
Why do they do this? Because games aren't complete 6+ months before launch. A lot of things in the game might still be incomplete so they can't show any meaningful lengths of gameplay without some placeholders, glitches, bugs, framerate drops due to unoptimization or just plain unfinished level/enemy designs popping up.
THIS IS EXACTLY HOW A LOT OF GAMES HAVE BEEN MARKETED IN THE PAST. The first gameplay trailer really doesn't show anything too meaningful, they are the trailers that usually just show us a bit of the setting, the characters, roughly what they think the final game will look like in terms of graphics and some absolute basic gameplay (or somewhat faked gameplay, in many cases). The lengthier gameplay demos come afterwards as they get closer to completing the development and releasing the game. They will show a lot more (but still not all) of what this game has to offer at E3, 100% surely, and it WILL be more than what you saw now.
Why are they showing this exact moment of The Order? I don't know. It seems to be early in the game, so maybe it is to avoid story spoilers for now. Maybe it's because a lot of the game is still unfinished and this was the most finished portion of the game. Maybe it's because the game is still probably 6+ months from release so it makes no sense to start blowing all of their load on the marketing of the game. Maybe it's because this short 15-20 minute segment the clips are taken from is just short AND lengthy enough; short in a sense that it could be shown to the press easily without having to resort to a 2 hour gameplay and spoil much of the game, lengthy enough in a sense that it showcases many of the gameplay and other features of the game in a short enough time span (i.e. this shows interactive cinematics, a bit of story, a bit of shooting, a bit of QTE, a bit of banter between main characters, a hint of one faction of enemies in the game, a bit of the kind of in-game eventst the game might have etc.),. Maybe it's because of all I've described above (or none of those).