EF I believe you are correct on a technical rulebook level. The player was not contacted. However the refs can overrule this by deeming the intercepting player as "giving himself up" (taking knee with no intent to advance the ball) after the interception, thus the play is dead. Had the player got up and moved forward and then the ball got batted out of the endzone it would have been ruled a touchback. Wait who am I idding? These refs have conferences after every play and then do whatever they want.
From what I've seen a player can give himself up in any part of the field. I've seen it on interceptions at the end of games where he falls to the ground, the play is then over.