I was thinking that too, but the Treasure near Whiterun (Treasure 4, which I've found) isn't where the Hard Copy Map has an X. It's not far, but it's not the same spot. And the in-game treasure map was spot-on.
Someone just told me it may be rune stones, bur that does not match up to the rune stone near river wood
I hope someone has gone there to test this out