Probably because it's relative to the other TE archetypes would be my guess, they all have different niche roles. It's just a balancing thing
Possession TE has catching at 90, speed at 85, agility at 80
Balanced is at 85, 85, 80
Vertical is 80, 90, 85
So if you compare it to the receiver builds, vertical is closest to the speed receiver who has lower hands than all the others at 90 (other than route runner, which is also 90)
Idk it kinda makes sense to me
EDIT: RBs can be receivers too look at McCaffrey and sometimes Le'Veon Bell and Reggie Bush back in the day
Possession TE has catching at 90, speed at 85, agility at 80
Balanced is at 85, 85, 80
Vertical is 80, 90, 85
So if you compare it to the receiver builds, vertical is closest to the speed receiver who has lower hands than all the others at 90 (other than route runner, which is also 90)
Idk it kinda makes sense to me
EDIT: RBs can be receivers too look at McCaffrey and sometimes Le'Veon Bell and Reggie Bush back in the day