It appears that some of the subsequently missing features were shown to journalists such as Destructoid's Jim Sterling who states: 'I feel lied to. I spoke to (Gearbox's Randy) Pitchford about Aliens: Colonial Marines, and he talked to me about the game's "next generation lighting" and other awesome features. He promised things I never saw, he showed a room full of writers things that would never make it to the final product.' Other sites have also picked up on the controversy, including VideoGamerTV who released a video highlights some of the major differences between the demo and final release.
However, the shenanigans don't end there. There are in fact four companies credited with having developed the game, and it's unclear just who, if anyone, came up with the lion's share of A:CM. There's been a lot of back and forth regards this issue, as noted by MCV. One post on Reddit, supposedly from an inside source, even goes so far as to suggest that the game was pushed through certification to avoid any potential legal backlash from Sega. Whether or not the truth will ever come out is anyone's guess.