He is not leaning on people he is reading the blocking then finding the ball carrier. In a read and react defense your not going to often see the DT or NT roar up the field, but rather hold the point of attack then provide pusuit, or mess up the blocking scheme which is just what this kid does.
In the HUDL highlights he is way more active because he has better understanding of the read & react schemes and improved strength from being a year older. In coach D's scheme this is what you want your dline to do in order to keep the LB's clean.
Also this guy has 3yrs to play 2, Also notice in the Hudl highlight he demonstrates high football IQ by diagnosing plays quickly an knocking down passes when he can't get to the QB. Or in 4 plays when he is losing the battle at the point of attack, rather then give ground you see him drop to 1 knee in order to create a pile in the running lane and he then gets in on the tackle.
Last year we say D smith look like he was on roller skates going backwards, instead of droping to knee to cause a pile in the running lane. This kid also plays with a fire, that can get the rest of the d-line hyped, watch the hudl highlights.
Go Canes