I think a lot of this is from the fantasy world and they are harping on a few comments from reporters during camp. Fantasy tends to echo the comments until they become the story vs a notation. They are also using the 3rd round pick as "see, they don't like Devin".
In real football, I expect a nearly even split between the two over the season unless one breaks out as clearly better. It will be hot hand/team specific on who get the most carries in an individual game.