I think they have to be flat-climbers. The percentages we used for flat-climb in the GV-lists, don't compare to the flat-climb-icon (which relates to the star-system).
Flat-climb icon: Only Climbing, flat, stamina and teamwork matter.
Flat-climb GV-list: Climbing, flat, stamina, downhill, technique and teamwork matter.
My guess is that Pipiolos' climbers, will have relatively low stats in downhill and/or technique.