Solution

Rui racked his brain as he thought of a solution. He couldn't rely on the VOID algorithm. He couldn't really rely on his techniques alone. Their physical parameters were identical.

WHOOSH

Rui barely managed to evade a strike. ('The only difference lies in mind that is controlling the mental bodies if the second hypothesis is correct.')

If that was the case, then Rui very well might have a tactical advantage. If not, then he could reasonably be assured that the first hypothesis was true. After all, what were the odds that the symbiote that was not supposed to be genuinely intelligent or actually sentient had the same degree of tactical intelligence as him?