Maro Itoje is instantly recognisable to me, as a Saracens season ticket holder for many years, and a regular Twickenham goer (plus he’s the best blindside in the world- and I’ll even stick my neck out and say he’s the best player in world at the moment), but honestly, I wouldn’t be able to pick Rashford out if my life depended on it.
So if Williamson follows neither sport, perhaps he simply doesn’t know (although, as he was talking to Itoje, he should have had the respect to find out who he was talking to).