I think this is less about a motion detecting camera and more the sudden jump in bitrate needed to encode all the new information when the scene changes quickly. This also lets them stimulate the camera at a known frequency, which I think could get them a better snr vs random emissions. unsure on how h264 or etc is actually encoded in terms of memory access patterns though
If the goal is to stimulate a H264 encoder or similar waving a theoretical big orange square around in a room will equally accomplish the same task. Though admittedly you can get some pretty damn powerful flashlights with multi-pattern strobe features for $35 (running on one 18650 or 21700 cell), so strobing a room isn't technically difficult or complicated either.
