Khan had gotten stronger after his fight with Major Veril. He had abused the blue plants' properties and completely mastered the Lightning-Demon style. That was no small power-up, but the other side of the hall couldn't be underestimated.
The guests didn't bring random fifth-level warriors. Those soldiers were noble guards, the Global Army's true elites, and the hall had eighteen of them. As incredible as Khan was, that probably was above his limits.
Nevertheless, Khan wasn't challenging the guards to a fair fight. He wasn't even putting himself out there as a warrior. He was a walking calamity, and the soldiers realized he would never lower himself to their level.
The noble guards' lack of heightened senses didn't imply ignorance. They could almost feel how powerful those floating spears were, and their number prevented them from underestimating them. Truthfully, the soldiers had come prepared for a similar instance, but the risks remained massive.