The Gwynedd Archaeological Trust cites the summit cairn of Pen Llithrig y Wrach as being of Bronze Age origin (PRN 3799):
‘A low, flat-topped cairn 4m diameter with a turf cover over small stones, is on the summit of Pen Llithrig y Wrach at 799m. A number of edge-set stones protrude through the eroded surface.
Sources :
Archaeology in Wales , CREW, P. , 1980 ,
Prehistoric Funerary and Ritual Monuments: West Conwy/North Gwynedd , SMITH, G. , 2002‘
I concur, the construction and positionning making this likely in my view.