I (for what it is worth) believe he thought he was in a tail stall situation.
I wonder if Colgan's DHC-8-400 ground training included watching one of the NASA ice contaminated tail plane stall videos.
NASA has done some stellar ice contaminated tailplane stall research, and produced several great tail plane stall videos, but some operators with aircraft that are not prone to tail plane stall use these videos in their training, without also stressing that their aircraft type has no known susceptibility to tailplane stall. I currently fly two aircraft types that are not prone to tailplane stall (many hundred of each type in service, with no tailplane stall accidents or reported incidents), yet each year in recurrent training for each type I watch a NASA tailplane stall video.
Yes, pilots should know about ice contaminated tailplane stall, but training should cover the specific risks for each aircraft type. If a type has no history of tailplane stall, then the cold weather portion of recurrent training should focus on other, more relevant, aspects.
If you are flying DHC-6s, Jetstream 31s, etc you need to be very aware of tailplane stall, what limitations and procedures must be followed to avoid it, how to recognize it, how to recover from it, etc. If you are flying types with more recent type certification dates, there should be no susceptibility to tailplane stall, if AFM limitations and procedures are respected.