FWIW. I see the “right shoulder” as a hip as well. The ape is either prone or leaning far forward in an attempt to pull away from the little man cutting off his limbs, so that from the viewers perspective the hip is behind the arm-stub. Conan has his foot on the right side of his neck.
I think the reason it looks weird is that the neck is at a weird angle, which is kind what it actually would look like if you were trying to swivel your head around to look at someone standing on your right shoulder, but because you can’t see much of the rest of the body of the ape it looks weird. I suspect when the artist sketched it out, more of the ape was visible and it looked better. Indeed, in Minces’s link, just adding an inch makes it look a little clearer since you can see the real left shoulder.
I’ve never read the Conan books, are they any good (excepting the poor cover art)?