The video is not a "study", and I'm not sure why the second "rider" is standing up with a kids' bike between his legs; so I wouldn't take it seriously.

The cited article (and some cited pieces in its lit review) does suggest a <3% drag reduction for the leading rider in a two-person paceline, under very ideal conditions. (i.e., a drafting distance of a few inches.) I didn't see any numbers as high as 4%.

And at any rate, neither of these sources supports the conclusion of a 1-2 mph increase for a leading rider in a two-person paceline. Drag and speed are two different things, and we'd need someone who remembers more about their college physics to sort that out.