"Some" is a lot different than "all." I've admitted that "some" (a very small amount) of the horizontal velocity could be converted in vertical and I explained how that could happen. You, on the other hand, seem to believe (with apparently a similar "faith" to which you cling to your beliefs about helmets in general) that there is a way to convert much more, if not all, of a cyclist's horizontal velocity in vertical. You have yet to explain how that can happen.

So, please, explain to me how a 15 lbs. bike that is not anchored to the ground can generate enough centripetal force to swing a cyclist down towards the ground. Keep in mind that if this did happen, whatever horizontal velocity the cyclist had would all but end (depending on how much was converted to vertical) meaning the cyclist would appear to stop in mid-air, much like a gymnast on the parallel bars swinging from one to another. Anyone who's ever watched that discipline has surely noticed the immense arm strength those athlete's posess in order to do what they do. There's a reason for that strength and it's the centripetal force that is missing from the cyclist/bike/pothole scenario.