You guys dont seem to realise you CANT judge rolling shutter by filming a monitor with a second camera.
You have the native rolling shutter of the actual camera.
You have the refresh rate of the monitor its being fed into with HDMI.
You then have the rolling shutter of the camera filming the monitor.
Thats a compounded 3 layers of lag and NOTHING like what the cameras actual rolling shutter would actually be, and I'm really surprised anyone would even try it.