Pitching Velocity vs Pulldown Velocity?

Hello. I am 15yrs, 5’9, 170lbs. Early in March this year, I threw 69 everytime on my pulldowns and 72 on my fastball when pitching off the mound. I have not been clocked since but I feel like I still throw a fair amount harder off the mound instead of a running throw. I am definitely throwing way harder then I was in March as I can hear the snap in glove a lot more. And the ball travels for way less time. Just wondering why I throw harder off a mound instead of a full cro-hop?

Posting a video of both deliveries would be helpful.

Good question… one to which I unfortunately do not have an answer… my son is the same way. He throws harder off the mound than he does doing pulldowns with a 5oz ball. However, the velocity “gap” between the two has become narrower… I do believe the pulldowns have been a strong contributing factor to the velocity gains my son has achieved. He does the Driveline program and follows it religiously.