Hula, do you mean the bit about where he asked her age? It was on the link lower down.
I do think that asking her age indicated that there was some doubt. The fact that she dodged the question should have made him think a bit harder.
I do agree that this is different from knowingly forcing sex on a 10 yo; nevertheless, he was at the very least negligent and/or indifferent to her age and has paid the price.
The fact that he was visibly shocked might be more to do with her actual age, i.e. 10, than the fact that she was underage - which he probably guessed.