That point aside, the officers in question should NOT be charged with false arrest or "imprisonment" for executing a "technically correct" arrest.
I understand the argument for hassling habitual troublemakers in the interest of public order, but they’re not supposed to wind up near-dead before they reach the station. I wonder if the screwup was that Freddy was acting out, so they restrained his feet,. Without buckling him in, that could have made him more vulnerable to van stops and turns— he could easily trip and be unable to protect himself. Separate issue from the pocketknife beef, of course.