So, in Evangelion 3.33: You Can (Not) Redo, Shinji is forced to wear a Deep Synchronisation Suppression choker around his neck that, as the name implies, will explode if it detects synchronisation with an Evangelion unit.

Near the end of the film, Kaworu takes it off him and puts it around his own neck, which ends up killing him. This observation came from a friend of mine, but analysing the scene, you can see that the choker doesn’t do much when taken off Shinji.

So I ask: What’s the actual security on the device? Why couldn’t Kaworu, at an earlier point in the film, have taken it off and thrown it into the abyss?