Upon seeing only a single body, the Saint stage cultivators furrowed their brows. Since there was only a body here, then this meant that the other had been slain. As in, his body had been reduced to small fragments. But they weren't also sure if this body before them was dead.
It was just that Alex was unconscious. If he wasn't, and they sensed the cultivation stage that he was in using their cultivation percipience ability, they would be shocked beyond any word would be able to describe. So now that he had blanked out, his body didn't produce pulses of power that would enable them to know that he was in the condensation stage.
So they thought that he was a saint-level competitor like them. And from the robe he wore, they could see that it was very expensive, judging from the quality of the material used in making it, therefore they inferred that he was a rogue cultivator.