I have just re-read your post and noticed you also mentioned Hobajon' Cross . This is also part of the Butterdon Hill row. Memory not what it used to be.
I was just a little concerned that people not familiar with the moor might get a little confused over a stone pictured on the Butterdon site but actually on Piles Hill. As you say the row runs between both.
Do you have any thoughts on the triangular upright?