[Yulanik]

I don't think timing has much to do with reaction since after a long period of time the mind no longer has to "react" but instead it becomes something like riding a bike.

IMO, it all boils down to muscle memory. Lots of people can time good because they can have so much muscle memory to be able to coordinate all of these notes perfectly without messing up, that's pretty much the difference. You can't have good timing without muscle memory.