They're not carved, but they may have once been used for axe grinding/smoothing, but if so, I think it was before they were stood up.
You're right SL, the Wallington stone was moved from about 6m NE of the Poind. I suspect Middleton was originally nearer the Poind too, but only got half way before the romany stone-shifters realised they weren't going to be paid extra. The Trevelyans of Wallington were pals with the Swinburnes, and robably felt they needed an 'Ancient British menhir' to keep up with the Joneses. They hung about with Pre-Raphaelites, which probably didn't help.
A couple of other snippets that may interest you in your ponderings:
1) A bit of literal trans from Bede implies that 'Poind/Poond' may have referred to the stars known today as Libra. (Apparently. I don't speak Saxon, so don't take my word for it)
2) It was that Capability Brown character who was responsible for the destruction of Nunwick circle.
