Man, that page 15...
He makes this very clear, though: he sees her as a child.
I'm old, and the difference between "somebody I would bang in a fantasy," and "child I deeply care for" is like night and fucking day.
Those are two very distinct categories, and they are utterly separate.
That said, he has no fucking business seeing her as an actual child; she's an adult, and he has no business judging, or setting conditions on, her status as such... unless she truly was deeply immature in some way; but she's not.
She's gone through horrible trauma, and is absolutely an adult because of that.
Let's hope it's just seeing her as uncomfortably young for him, personally.