That's going to be entirely up to Crouch. Tennessee and the other schools recruiting him have left that open-ended, as far as I can tell, and if he wants to play linebacker, that's probably where he's going to get his first look wherever he goes. He still hasn't made up his mind on what he wants to do there, so most of the teams he's considering really haven't zeroed in on either side of the ball. If you recruited him as a RB and then he decided he wants to play linebacker, you'd basically be eliminating yourself for maybe no reason. But it's worth noting that Crouch told me back in late August that he thought at that time that the Vols wanted him more as a running back. That was just his interpretation, though. They hadn't straight-up told him that.
On the running backs you mentioned, I wouldn't say Tennessee is "broadening" its board. Witherspoon and Mimms are guys the Vols have been evaluating for a while, and they still haven't offered either of them. If they start handing out more offers at RB, perhaps that will be something to read into, but right now I don't think anything really has changed there. The bottom line is Tennessee wants a running back in this class, and the Vols probably can't count on Crouch being that guy even if they get him, because he's not really sure what position he wants to play.