I think it's just he is extremely quick , and because he's 6'6 , he's able to reach his top speed extremely quick , so he might max his speed out in 10-15 yards.. On top of that, he runs so physical and is extremely agile for a guy that size.
What he did to Barr , considered an elite lb , considered a very fast and athletic lb was amazing. The dive, hurdle and stiff arm displayed his speed , quickness,agility , and just awesome physical running style. Barr had to be shocked that this giant QB can run like that .
????
How did he not go # 1? To run AND throw like that is a cheat code.