The biggest problem with Jackson's hit was the fact that when he made contact, Jackson himself was entirely out of bounds. Yes, Hurts had just barely put a toe out of bounds when Jackson went to make the hit, but by the time the hit was made they were both clearly out of bounds, and I would want that flag every time if it were Caleb getting hit.
I wouldn't call it dirty by any means, but just over the line of what draws a flag. And it was worth the yards given up because Hurts definitely wasn't the same after