Flash doesn't have to be faster. Max flash sync speed means up to this speed the shutter is guaranteed to be fully open when exported flash signal triggers the flash. Below this speed is totally fine, above this could result in partially lit images.
e.g. A camera's max sync speed is 1/60s, and you connected a flash unit over sync cord, and set the camera to 1/250s, ignoring the lightning bolt sign on the dial. You take a picture, and alas, top half/left half is pitch black and only bottom half/right half is shown correctly, because you exceeded the max speed and mechanical circuit to trigger the flash did not close until image was already partially taken.
Or, e.g. A camera's max sync is 1/80ksec., with a random flash unit on top. You set it to that 1/80ksec, push down the shutter, the camera triggers flash, flash starts discharging energy onto Xenon gas tube. As the light intensity goes up, the image processor on the camera pulls down internal !global_shutter_trigger signal to lock image data onto per-pixel RAM on the sensor. 1/80ksec. later, the signal is released and intensity is recorded for retrieval.
These faster sync speeds are useful for situations when a) you want to use flash && b) the room/environment is too bright for a flash. Now you can keep ISO value to not way low, aperture kept open to F2.0, etc. without overexposing the image(can't do F0.3 at 1/80k; aperture is limited to up to F1.8 with some body recognized lenses attached, according to product pages)
e.g. A camera's max sync speed is 1/60s, and you connected a flash unit over sync cord, and set the camera to 1/250s, ignoring the lightning bolt sign on the dial. You take a picture, and alas, top half/left half is pitch black and only bottom half/right half is shown correctly, because you exceeded the max speed and mechanical circuit to trigger the flash did not close until image was already partially taken.
Or, e.g. A camera's max sync is 1/80ksec., with a random flash unit on top. You set it to that 1/80ksec, push down the shutter, the camera triggers flash, flash starts discharging energy onto Xenon gas tube. As the light intensity goes up, the image processor on the camera pulls down internal !global_shutter_trigger signal to lock image data onto per-pixel RAM on the sensor. 1/80ksec. later, the signal is released and intensity is recorded for retrieval.
These faster sync speeds are useful for situations when a) you want to use flash && b) the room/environment is too bright for a flash. Now you can keep ISO value to not way low, aperture kept open to F2.0, etc. without overexposing the image(can't do F0.3 at 1/80k; aperture is limited to up to F1.8 with some body recognized lenses attached, according to product pages)