This does not make sense

[Little Blue]

Typically, or as much as my understanding permits, an unsent needs to be severly weakened before they can be sent. Auron is one of the most strong willed unsents going so he needs either the pulp being beaten out of him before he can be sent, or they need to be willing to be sent.

I think this is also why Jyscal returned after being sent. His will was so strong that he clawed his way out of the farplane to tell the world about Seymour, only the action of doing so weakened him enough to allow him to be sent... again... You'll also notice in this scene, Auron collapses, an indication that the sending might be affecting him at this point, coupled with his proximity to the farplane.