Just did a quick Google of weather patterns in Bermuda. Apparently, they average 5 to 7 inches of rain per month. With very little fluctuation. Rain is sudden, heavy, and short-lived. That may kind of make sense for the roofing strategy then.

I think that's incorrect, to a certain extent. Increasing the overall surface area of the roof increases the volume of water that can be on it at one time. Each of those ridges would act as a cistern capable of holding a volume of water that would have otherwise overran a simple slope. Instead of a straightforward through-rate, you need to take into account many small pockets of internal storage. Depending on the frequency and intensity of rain in the area, that could be significant.