I was wrong.
All along, there were never any extra sentences explaining weaknesses at the back of the Beast Index entries. It was just that when I was reading the materials, my mind was working too swiftly, too smoothly, like seeing the problem 1+1=?, and instantly realizing the answer is 2, subconsciously filling in the standard answers for the weaknesses.
The mental process was so smooth that I ended up with memory gaps, similar to the Mandela effect.
For some beasts that required calculation and reasoning, he didn't take them too seriously either, because it wasn't too much trouble to come up with an answer with just a minor mental pivot.
He overlooked this seemingly insignificant detail.
After this chat, a small doubt in Ren Zhong's heart was resolved.