I think that for smaller cheeses (using the 4 inch hoops he provides in his kits), it will eventually get some blue veining on the interior without spiking. For larger cheeses, you should spike it.
Steve's put out an 'update' to his book that talks a bit about it:
"If you’ve ever bought some English Stilton Blue Cheese, you may have noticed small little holes in the exterior. Since many English Stilton’s are made large, about 17 lbs., holes are pushed through the cheese to allow the interior to ‘gas off’. This also allows the blue veining to spread throughout the interior of the cheese. You may or may not want to do this with your cheese. Having made many blue cheeses using one gallon of milk, I have noticed that without pushing holes in it, blue veining eventually resulted. "
