I take it to mean that, as a man, the eternal Logos had to be tempted in every way we are, to progressively obey where Adam did not, at every stage of human life, to redeem and glorify all people regardless of age. Heb. 4.15
He could have just been considered all-holy as He truly is, but then again, what would be the point of His incarnation?
He wasn't Superman. He was true God and true man, at every stage of weakness and development in which we progress. He took on our limits as souls and bodies created in a womb, circumscribed beings. Of course He was sinless since His conception, but man's union with God requires the deification of every stage of life, especially for Jesus to be a new home for us all.