With all deference to your Huw-ness, I will render the following on leaf shutter synchronization.
First, I don't take camera equipment or watches apart as I seem to have a better talent for losing small parts than reassembling the item. So, I have not personally ever taken a large format shutter apart to see or test how it synchronizes - nor do I intend to for the above stated reason.
Secondly, I can only go on what I was taught in photo school, the information in my photo books, and 35 years of experience.
What Stroebel says about synchronization is as follows:
"It is sometimes assumed that because of the short duration of the light from electronic flash tubes, none of the light can be cut off by the shutter and the guide number will remain constant at all exposures."
"...makes it possible for the shutter blades to close soon enough to prevent some of the light from reaching the film. A test made with one type of electronic flash unit revealed that only 59% of the light was transmitted at 1/500 of a second compared to 1/100 of a second and slower speeds..."
"Changing the exposure time setting from 1/30 second to 1/500 second reduces the light from a continuous source to approximately 1/17, but reduces the light from flash lamps to approximately 1/4."
Lastly, all shutters (focal plane or leaf shutters) have a built-in synchronization delay. With a leaf shutter, it can be as long as 30 milliseconds. What the designers are trying to do is get the shutter to the fully open portion of the total shutter open/close cycle before the flash is triggered as you stated. This requires a delay.
My point being that unless the shutter has a continuously variable delay (most that I know of don't do that), you are better off to use slower shutter speeds with an electronic flash. Or, you will need to do testing to see the change in exposure caused by the faster shutter speed.
Heck, I could be wrong, Leslie Stroebel could be wrong, the Langford Manual of Photography could be wrong - but...
This has been borne out in my own inadvertant (OK- mistake) electronic flash exposures. When the shutter was set at 1/250 with the correct f/stop, the transparency appeared about 1/4 stop under exposed. When I changed the shutter speed to 1/15 second with the same f/stop of the same subject it was correctly exposed.
However, as someone once said, "your mileage may vary with usage..."