You are right about the starting torque being low at start. In a centrifugal pump, the required torque is proportional to the square of the RPM of the impeller (HP is proportional to the cube of RPM). So at start it is zero and climbs as the motor spins up so it is a perfectly fine design for a pool pump. So a PSC motor pump will start just as quickly as any other motor, at least what you can notice.

Also, most high efficiency motors are either PSC or CSCR (capacitor start, capacitor run). Both keep a capacitor in the starter winding to minimize the EMF losses and improve efficiency. The CSCR motor has more starting torque which really isn't needed. However, the run capacitor can be tuned in the CSCR for better run efficiency where the PSC motor requires a capacitor for both start and run situations. So the efficiency of the CSCR can theoretically be a little bit better than the PSC although from the CEC published test data, they are not all that much different. Personally, I think the PSC is better design since it eliminates one of the primary failures in a pool pump, the centrifugal switch so it should have better reliability.