According to Gwynedd Archaeological Trust, the pony path is a public footpath 'which has slate backed steps in places.' The track is marked as a pony path on modern editions of the OS map and a "BR" (bridle road) on the first edition of the 25 inch OS map, published in 1889.
Sources: Gwynedd Archaeological Trust database, reference number 13614 and OS maps.
M. Ryder, RCAHMW, 4th October 2018.