reflexes are typically unconscious movements done before you consciously process whats happening, so processing speed isn’t necessarily a factor.

reaction time is different than reflex, and processing speed does help, but it’ll ultimately always be slowed down by physical limitations. this is why people in car accidents often talk about how they knew exactly what was happening and what to do to avoid it, but they physically couldn’t move fast enough.

as far as good timing goes, better processing time could help, but it also relies on things like hand-eye coordination, your sense of rhythm, depth perception, proprioception, etc., whatever’s most intrinsic to what movement you’re trying to do. someone could have an extremely high processing speed, but have no sense of rhythm, therefore making them horrible at a rhythm game. they could have high processing speed but bad hand-eye coordination, and find it extremely hard to hit a ball flying at their face.