Marcus is a tough, competitive guy. He lets his feelings talk, just like Draymond Green did with KD earlier this year. Both were "right" about the argument, from what I can see.
Now, he might be going a bit hard on the Rookie. Rookies make mistakes. I guess Jaylen saw an opportunity to drive to the basket and took it instead of runing the play. C's were up 13 with 7 min left to play, maybe he thought the deal was sealed.
Anyway, I don't think there is anything big behind that. Marcus could have gone softer, he didn't... meh.