You obviously don't know the kid, or not as well as you think you do. As I said, he has matured a lot as a player. Kids do mature as they grow older; I know you already knew that.
He has pushed the boundaries with his niggle in the past, but he had his mind well and truly on the job yesterday. A bit of niggle is OK if it results in a penalty to your team but a player needs to know how far to go and keep control himself, otherwise it backfires on you.
Don't get mixed up about the difference between arrogance and confidence. Sometimes it can be a fine line especially with young people but there is a difference.
He's been punching above his weight for a while now (metaphorically speaking). He's not the biggest kid on the field and never has been but he isn't scared, so the 'one day he'll bite off more than he can chew' has already come true. He still competes. As a smallish 15 year old he competed against well developed 18 year olds all last season; and he wasn't stuck out on the wing somewhere. He played fly half where a lot of the traffic is. I didn't see him take any backward steps.
If he wasn't willing and aggressive to a certain extent you'd be bagging him for not having a go.
Anyway, have a look at the video and work it out yourself. If he was an aggressor in that skirmish yesterday I'll eat my hat. I'll eat yours too.
I thought he had a good game yesterday. He played smart. So did all the Waverley backs.