Surly uses 26" wheels on all the LHT's under 56CM. They said the wheels are more durable and easier to find.
But that's neither here nor there, Surly designed the LHT's (all sizes are available now, not just the short ones) around the 26 inch wheels. That's an entirely different thing than simply sticking 26 inch wheels in a frame designed for 700c. While there are some benefits to 26 inch wheels, they are far outweighed by the trouble caused by converting a frame to a size it wasn't intended for.