“He is admitting to having pornography, but denying the criminal child porn charge.”
No.
Most were adults.
Some may have been children.
“He reportedly admitted to distributing the pornography but claimed that most of the images were of adults, while some may have been of children.”
By saying “some” “may” have been children, he establishes his position that he does not know - therefore he did not “knowingly” exchange underage pictures.