I've no doubt about this one - Coflein are well known for being reticent without excavation, but would you really believe the third of the great trio of main Brecon Beacons summits would not have a burial cairn?
The Clwyd Powys Archaelogical trust have no doubt either, having recently completed a survey of Prehistoric Funerary and Ritual Sites in Breconshire and - not surprisingly - the Cribyn cairn (ref PRN4560] is in grave danger of vanishing under the onslaught of walkers boots. I'll post the link on the page.