Pneumatic turrets using a hirth or curvic coupling are far sturdier, but as you're aware, they are far more complex (and good hirth/curvic couplings are not cheap!).
They have the benefit that the tool disc gets clamped firmly in place with lots of mating surfaces, whereas on a ratchet and pawl setup, not only do you have flex due to the shaft needing to be able to rotate, you're relying on a single point of contact to resist cutting forces.

And as already mentioned, parting is where you're most likely to notice any play/flex on a lathe.