The beer cans help show all pistons in the mid-range travel position with cam/drive gear marks aligned. Is this correct? It must be since the video shows spark for all 4 cylinders at TDC.
Most other engines I've worked on have piston #1 at TDC when timing marks are aligned. This just seemed odd to me, but again, this appears correct.
And it was fun emptying the cans after verifying timing :)