This example of an AC supplied LED clock is really about the effect of mains power frequency and stills photography, but I thought it interesting, and something that could easily affect video. Shooting high frame rates for slow mo for instance. I imagine that mains powered LED video lighting is, at the very least, rectified, and most probably, smoothed into a reasonably clean DC power supply.

FZ28 Shutter Speeds Test (Spinning LED Clock) - YouTube

Looking at the video again, I see it is a 'spinning' LED clock. I don't know if the effect is unique to this type of display or any AC fed LED.