You can count from a still picture or a video segment and use that to test or calibrate. So it may just be inaccurate reporting to give the impression that the

You can count from a still picture or a video segment and use that to test or calibrate. So it may just be inaccurate reporting to give the impression that the calibration depends on humans surveying live action, which is exactly what they are working to replace. If the researchers publish their results the exact methodology used will tell but I assume they are competent.