I believe they do.
The only problem with CO2 is that it cools down quickly. It would have to be 75 degrees Fahrenheit or warmer for it to maintain any kind of power. As it cools CO2 loses power and shots get weaker.
Of course if you wait about 10-20 seconds it will go back up. This would only really effect guns like the ones you posted in the video. The fully automatic guns that have blowback which uses more gas.
The little puff of smoke or vapor leaving the gun makes me believe it's CO2 cause CO2 will do that. It could be green gas which as someone said is propane. I don't think it would lose power at all.
So the gun in the video uses green gas. I wonder what is causing the vapor/smoke to leave the gun? Maybe lube they use?
It's pretty cool.