H502 doesn't have any collimator. I believe you didn't remember that the light intensity (spatial distribution) is not constant to every direction. It is highest straigth forward, and drops to ~50% at 60 degrees (120 degree beam). There might also be some extra losses in the periphery due to reflections from the glass.
There is no collimator. If they chose to use 80 degree beam, it would have just meant a tighter collar and the light from the extra spill would be lost. It could be collected with a collimator, but then the light wouldn't quite be a pure flood light any more, and the body would be longer, too (maybe as long as H51). With current design, I believe there is no space for a quality reflector or lens.