top guy to go wherever the top wr goes.

The boundary or field thing isn't standard by any means. If your top guy hates playing on the left, why play him there if it's the so called field side? Or the easy side for the QB is his right, if he's left handed. Sometimes coaches like placing their top guy on the left for this reasons.

I guess I'm simply saying that there are a lot of options and reasons to do what you do.