You absolutely do not have to be tall to play false 9 or even a straight 9 in modern football.
Look at City and Guardiola, they prefer shorter strikers in Aguero and Gabriel Jesus (both shorter than Dybala) because they have that explosiveness that fits the fast combinations.
Sadly Dybala does lack in that area but that does not mean he could’t do a proper job in that role. Just give him a chance as he had quite a nice preseason.
Some in this forum act like he’s some sort of scrub Amauri style and forget that he actually scored 57 goals for us in 128 games. A goal every other game and that statistic includes his horrendous last season. Which btw strikes like Drogba and Benzema also had 5 goal seasons and then bounced back to the 20s. It happens sometimes.