FrameSync is only required if using the light for strobe or other fast flashes, and is not required for flicker-free continuous lighting, even when shooting High Speed.
All Creamsource fixtures have the ability to take a Camera Sync signal, which is used to synchronise any flashing or strobing lighting effects with the camera shutter. We call this feature 'FrameSync'. FrameSync has nothing to do with flicker-free shooting at high speed.
FrameSync is NOT required for normal High Speed shooting, when using the Creamsource fixture as a continuous light source. If shooting at frame rates above 200fps, it is recommended to put the Creamsource into 'High Speed' mode to prevent flicker, but it is not necessary to connect camera sync.
The Vortex fixture can be used at up to 5,000fps in High Speed mode with no flicker (depending on camera shutter angle - testing is advised).
If you are doing strobing / flashing effects and want to either avoid torn frames (from rolling shutter) or synchronise the strobe with the camera frames, then this is when you would need to use the FrameSync feature.