For real though, it's about what he does defensively, that's how I see a bit of Duncan in him.
Usually rookie big men are known to make their name purely off highlight blocks, and while he does do that, it's more about the little things: making the right rotations, not biting on fakes, being in the right place at the right time, and just willing to take on a greater role on that end of the floor. Rookie big men don't do that sort of thing. They don't have have that desire, experience and foresight. They're typically about making highlight plays on that end by showing off their athleticism. Mobley isn't concerned with that. That shows someone who's wise beyond his years, who sees the bigger picture, just like Duncan did when he was a rookie.
And while he most definitely does NOT have Duncan's refinement and scoring skillset
, he does make the right reads on offense too, and just knows where to be and what to do. This is evident in his passing, whether it be baiting the help defender into coming over and then passing to his assignment, or in the PnR either as the roll-man or as the ball-handler and finding the open man.