It should be obvious to everyone that Leavelle is grabbing Bookhout by the nape of the neck.
If he touched his shoulder on the way to the neck, so be it, but the neck was his destination. His purpose was to push him down, and it's hard to push someone down at the shoulder. You're on one side of him, applying force eccentrically, and you're more likely to turn him than push him down. But, when you get him around the nape of the neck, now you can apply force in the direction that you want him to go, which is down.
And, there was nothing essentially wrong with that. But, what should have happened next is that Bookhout's arms should have been twisted behind his back and handcuffs applied. So, why didn't that happen? It didn't happen because if it happened, then it would have been all over- for the scuffle. The men would have stepped aside, and Bookhout would have been stood up and walked away in plain sight, including the cameras'. But, since he was Bookhout, and he was pretending to be Ruby, they couldn't do that. He had to remain hidden. So, instead of handcuffing him, they kept the swarm going until they swarmed him into the building. It really was a ridiculous spectacle.
And note that it came out during the testimonies that several detectives involved in the Penguin shuffle had handcuffs. McMillan admitted having them, and so did Archer. And it's extremely likely that most, if not all of them did. So, why didn't they use them in the garage? Why did they wait until "Ruby" was inside the jail office? There is no logical or rational explanation for that. There is no talking point for it. My explanation is the only explanation: that they had to keep Bookhout under cover.