Yao Yuan was the most unique among all the Homo Evolutis, an All-Rounder. His uniqueness lied in the fact that other than Deceiver’s power, he had access to all the other Homo Evolutis powers, including the Whisperer.
The supposed Whisperer’s power was something that was hard to describe; it was something beyond scientific comprehension. It was unlike other Homo Evolutis powers. The Perceptor’s power could be explained scientifically as a heightened sensory sensitivity. The Diviner (the Sage was an exception) also could be understood as a heightened sixth sense. Even Animas and Thinkers technically could be explained scientifically. Of course, their validity is another issue.
In comparison, All-Rounders, Deceivers, and Whisperers were the most unique. We shall focus on Whisperers for now. Their uniqueness lies in the sense that when Whisperers used their power, they hear an indescribable voice.