The Stronglight roller bearings weren't tapered:



While a tapered roller bearing has lower rolling resistance than a cylindrical bearing (since the radius of rotation differs along the length of the roller, there is necessarily some sliding contact with a cylindrical roller; a tapered roller eliminates this), this was deemed inconsequential since headsets are not in constant rotation. Tapered rollers are much fussier about alignment than the cylindrical rollers, and the OP's picture suggests that even motorcycle headsets use cylindrical rollers.