Any source for actual difference in offered protection design? (There are helmets approved for both, given that the actual test requirements for the head protection are nearly identical. To project with the impact from about head-height to the solid ground below. That is, a fall.)

The cooling of the head, or keeping it warm, is the obvious difference in design. Most bike helmets are perforated nearly to oblivion resulting in very lightweight helmets. The helmets that suit both for both are too warm for sportive cycling, work decently for leisurely commuting with an upright bicycle, and excel as a winter helmet for such cycling.