By all means be devil's advocate, there might be something I overlooked or didn't know and then I will have learned something.
Point A: In MoH (2010), sp was built off UE3 while mp was built off of Frostbite so that's the reasons for the visual difference. (Were you referring to specific features?) BF3 is purely Frostbite 2.0. Is it possible certain Frostbite 2.0 effects will be scaled back for performances reasons in BF3 multiplayer? Sure, but if it can be done in sp I see no reason why it's not possible for mp as well.
Point B: The animations I'm mainly referring to are third person movement animations. They all look great so for it to be scripted, that means the entire gameplay video would have been scripted, right down to scripting what the player is doing in first person because his/her actions are dictating what the other players are doing (both teammates and enemies). The players in multiplayer won't have the little nuances like peeking around a corner and then looking at a friend for dramatic value and stuff like that but all the movement animations that a human player would enact like sliding into cover, peaking around a corner, kicking a door, sprinting, will most likely all be present in multiplayer if it it is present in singleplayer. And from these singleplayer videos, we can see it's already in the engine. I just do not believe that this ingame footage was faked. It doesn't have the glossed over cinematic look that a fake or concept video would have. A bunch of the effects in that video looked very similar to thing's we've already seen in the previous Frostbite engine. Like I said before, if it truly is a scripted sequence running in real time on the engine, then they did a very nice job of combining a cinematic into ingame footage which, if true, at the very least proves that the engine is capable of making the game look as good as these videos....and if that's the case, the only reason the end result wouldn't be like that is hardware limitation, which should not be a problem for PC's (consoles on the other hand, idk...).
I'm not saying my evidence is infallibly right and one should never really trust marketing at face value, but I think the evidence in this case points to this not being a full on fake, and if it is, it's probably the best fake for ingame footage yet released.