As I said earlier when a flash is working at high power output its discharge time can be longer than the faster speeds on a leaf shutter. Thus the shutter begins to close before the end of the flash. This appears to be what Stroebel is talking about, and is probably what you have experienced. However, for virtually anything other than full power output most flashes have much shorter durations that the fastest speed of typical leaf shutters, and will be unaffected.

I reiterate, for electronic flash the sync is triggered by the shutter blade mechanism reaching the fully open position. In other words, the delay you refer to is not something independent of the shutter blades, but is actually part of the same system. This is a direct mechanical linkage and provided the shutter is not faulty there is no way that it can fire the flash before this point. For M-sync it is a different matter. Here the flash is triggered at the beginning of the opening phase and the time to open may indeed have a bearing.