[The Might]

Indeed, Elladan and Elrohir makes sense since they had ridden as early as some months before the return journey through Dunland when they were part of the Grey Company coming to help Aragorn.

They probably remained close to the North-South-Road, but who knows, perhaps wandered off a bit into Dunland and would have thus been seen.

And of course they had often travelled into the Wild looking for Orcs, so perhaps they passed more often through Dunland.