The guy pushes on his forehead- the connection goes from his forehead to his butt-grounded.
The feet don't matter they are lifted off the floor like a sit up-maybe 6" or so. .
There are lots of old jujutsu tricks to show a developed connected body. Of course the real trick-is the connected body
I do one where I am facing forward and the uke pushes me over backward from the chest. So I am bent over backward with somone trying to push me up and over at a 45 deg angle. Its looks impossible since I am already going over in agreement with the push.....I don't go anywhere , and when I bring myself upright it feels like a crushing weight on uke. Doesn't work without connection.
Works great in the real world in motion too. When grappling with them trying underhooks or trying to take your upper body over your feet or forward like a seoi-otoshi or seoi nage.
In fact all of this works in any throw you can think of-not the least of which is hitting them or counter throwing