@Zoom Sci pointed out why he thinks Abed is imagining the timelines in another post, the point that made sense the most to me is that Abed imagined the Christmas claymation episode. I then furthered the thought that since he imagined the claymation due to having problems with not being at home for the holidays, he could be imagining this due to some problems he is going through. Perhaps between him and Troy, or him and the group, so he's internalizing whatever it is.
However, IN the claymation episode it's made VERY clear that Abed is imagining this and the group is playing along. There is no such indication in the alternative timelines episode at all. Within the episode, what evidence is there that Abed is imagining it? Or where is Sci's post?