@Meridis:
You forgot that the MC cannot see the full status of the fake priest.
E.g.:
The fake priest can use fire and water attributes which are opposing elements in this story.
The explanation he received is that humans cannot use the element opposite to their own.
So being able to use 2 opposing elements means that your real main element is a different one and hence you can use at least 3 different elements.
That is what the MC found out but he does not know the actual main element of the fake priest.
As such that can only mean that the MC cannot see the complete status of the fake priest.
Therefore there is the high possibility that the fake priest has some means of concealing his status so much that even the MC cannot see through the concealment completely.
And with that being the case we cannot be sure if the MC actually sees the real stats of the fake priest or if those values are just faked values to trick potential enemies into underestimating him.