I believe you're incorrect. The advantage of the solid is the lack of the hydraulic "shock absorber" affect. That inherant "squish" means spring rates have to be lighter and opening ramps have to be slower on hydraulics. Which is what usually leads to loss of valve control and "float".
A solid flat tappet ramp can be much faster and much more stable as a result. They have the capability to come close to rivaling roller cam profiles.
