Diptychs are an opposition of images, a comparison. This duality relates the two images but it also separates them. What becomes relevant is the connection between the two, the joint, being this connection conceptual or formal.
The two recordings on each diptych are of the same thing, recorded at the same time.
The two recordings on each diptych are of the same thing, recorded at different times.
The video on the left was recorded first. The video on the right was recorded first.