Following Aron's instructions, a panicked T'karsent out a scout to not just inform the other southern races about Aron's message but to also warn them as to how much of a threat he was.
Because she wasn't put under any oath, Aron knew she would ask the scout she sent to say more than what he had instructed. In fact, that's what he was hoping for.
If he were to restraint her to certain rules this early on, then she wouldn't act as freely as she usually would and may even fully submit. He needed the other races to view her as a victim still, she and her people needed to be that good of an example.
Komi were prideful and strong headed, thus they rarely negotiated. Conflict among them was commonly resolved through violence so Aron expected them to react the same way towards the invasion.