He never said he didn't know how to explain it, he just said he couldn't really explain it, sometimes there are things we can understand but can't explain.
Let me ask you this : Was Naruto ever asking Kurama to explain to him why/how/what Sasuke was doing? No, therefore he could have already understood, but Kurama was saying it so us readers could understand the situation.
You forget that he was still new with RSM then, therefore it could have just been because of inexperience.
And maybe he is? The Databook is not made by some fakers or fans, its made by people who work with Kishi, therefore it must be the truth, you can't say everything in the databook is false.
Name one technique that was made up in the databook, not a technique that was overhyped, but a technique that they made up without it actually being true.