Reading https://en.wikipedia.org/wiki/Polybolos, at least some of these used a windlass to rearm. That may explain part of the speed difference over one using a separate lever or one that’s rearmed purely by hand.
These weapons also may have given up on some firing power for firing frequency.
I'm not even considering the magazine reload time, just the time between shots assuming a full mag. That's 10 recharges either way, as shown in the videos. It's not like a machine gun where the energy is in the powder.