Has the databook remained consistent?
But that aside, all of the claims in the databook seem to be coming from the point of view of characters, not Kishi.
"was even called the 'Professor', and he still garners everyone's respect as the strongest Hokage in history"
-Was even called? By who? A character?
"the words used to describe the Third Hokage are filled with respect"
-Who is describing him? Kishi, or characters?
"The Third is called the strongest, even among the past Hokage, and he is even admired as the 'God of Shinobi'"
-More statements from manga characters
Can someone with a databook get a direct statement from Kishi about this stuff? DOesn't seem like he's asserting anything independent from the canon.