He was saying that as the hill was built up, the original centre would have become less important, or less obvious? to those building. So the burial would have ended up being a bit off-centre.
I was quite convinced but then.. Does it not depend at what stage the burial was inserted? I mean would you make a little mound first, then work on the bigger diameter and bring it up to the level of the little one (in which case it would be quite central, surely). If you inserted it later you might as well put it in the middle because it'd be easy enough to see where the middle was.
You'd think such a major bit of engineering would need careful mapping out on the ground, you couldn't just go adding a bit here and then a bit there.. wouldn't the Plan require quite exact behaviour or the whole lot'd slump?
OBviously I have no idea. but I'm not so sure about the Rev's argument now.