Okay, where are people getting this firm idea that a 36 MP sensor is going into a A7SIII of all things?
Sony already said themselves it's still going to keep that whole "low megapixels" part that was the purpose of why S has class-leading low-light in the first place. Seriously doubt their technology already evolved so soon for 36 MP to be on-par if not better than A7SII/A7III.
My theory on no official footage yet is more likely lack of budget to hire people on Blackmagic's part, like what "bigger" companies such as Panasonic did when they announced GH5s by handing it to Casey Neistat, Neumann and other filmmakers.