I recently heard a prospect Podcast and they dabated whether Julio Urias was to short to become a durable ace starter. Urias is 6"2
. The guy mentioned that shorter Starters are usually not as durable, especially if they are hard throwers (if you are a knuckleballer it probably doesn't matter but if you throw 95 and you are 5"11 they might think you won't Keep that up and rather Slot you as a reliever).
Of course it is possible to throw 95 at 5"10 if you are really explosive but those guys Need to use extreme stride momentum and hip shoulder Separation to reach those velocities. if that guy just loses a Little bit of flexibility or lower Body explosiveness his Velo will go down quite a bit while a 6"5 guy might be able to throw 95 with a more conservative Motion. just compare a guy like lincecum with Randy Johnson, lincecum needed a lot more Separation and explosiveness to hit his 96-97 than Johnson and he lost his fastball when he was in his late 20s (without Major injuries) while Randy could throw 99 at Age 40.