The solution here might be that it does mainly tell you they have constructed a coherent story in their mind, but that having constructed a coherent story in their mind is still usefull evidence for being true depending on what else you know abaut the person, and thus worth telling. If the tone of the book was differnt, it might say:

“I have constructed a coherent story in my mind that it is wise to take admissions of uncertainty seriously, but declarations of high confidence mainly tell you that an individual has constructed a coherent story in his mind, not necessarily that the story is true.”