You assume that Sasuke would never encouter an Uchiha until he gets a kid? No. Plus didn't Obito say that Itachi made it only for Obito's sharingan?
Wait, wut ?
Why would Sasuke amaterasu a random kid ? Well it's Sasuke...But still... ?
He means when Itachi put in the Amaterasu trap to be used on Tobito.
