There is such a thing as explicit sexual poses but I do not personally think these qualify. I found the pictures in both links artistic rather than pornographic. There is more child nudity in the average historic art gallery than the Boy book.
Nudity in itself can be viewed as art and only becomes sexual in the mind of the viewer. I can not know how Jackson perceived these pictures I can only comment on my own perception of them.
Jackson’s interest may have more to do with the loss of his own childhood - an attempt to relive the feelings of being a boy which the pressures of show business denied him. He built his Neverland Ranch to recreate a lost childhood which is a factor in how his interest in children may be viewed. Maybe I am being generous but I would rather that than wrongly accuse someone.