Flash isn't always that fast - only at low or mid-range power. At or near full power some units have quite long discharge times - longer than 1/500th at any rate. At full power my Metz 45CT3 has a discharge time of 1/300th, and I think (although I've never measured them) that my studio monolights are even longer than that.

OTOH, although the Copal 0 shutter speeds go up to 1/500th, there is a fair chance that they will be rather slower than that, so it may not matter in practice.