That play is either a call from the sideline based on defensive alignment tendencies or something that comes down from upstairs. If the defense plays an extra leverage player to the field or the offense has numbers short side.

If it was an audible the QB would call it based on numbers past the center to the short side, or the ability for the tackle to pin the edge based on alignment, which would also be in the call that sets that blocking rules. The WR then has to block his man and the QB can option off the secondary force player, assuming the DE is logged by the tackle. So in other words a lot goes into that determination that might not be apparent to most.