User blog comment:Paul.rea/Teen Wolf News 111114/@comment-98.66.192.133-20141115160059/@comment-4091815-20141116202629

They were pretty clear from the start that the season 3 split was the network's idea. The reason they did two different stories is because they knew there would be a several month gap between episodes 12 and 13 - It is difficult, with a serialized show, to sustain that big a gap without a major cliffhanger.

There is also the fact that they could sell two DVD sets instead of a single Season 3 omnibus.