@FredFriendly This is a dangerous argument to make, let me play devil's advocate and ask "Is it, really?". Granted, her characterization so far does say she would not go "eeeww", but such a fear is not unsubstantiated. Remember a key and connect element is not just him not revealing his lack of experience, but his emotional state. If we do replay this story with him outwardly showing his emotions with the same strength and intensity that has been playing in his head, what would be a realistic reaction?
Imagine if we re-played chapter 2 and he does show the full level of fear he is trying to control? What would be a realistic reaction? Now, within her characterization, she probably would not react in the way he fears, but be is fully readable by his friend - of which the range of emotions she felt from amusement to care for her friend, none of them imply attraction (now thinking about that, that might be a clue to why Kurata and Inoue seem to operate on such a closeness that Yamamoto would interpret the two as having a closer past - but seemingly zero attraction). Or let's take chapter 3, instead of his semi-controlled confession, what if he confess with the full eagerness and anxiousness, how does that tend to sound in a realistic context?
Maybe I'm wrong, maybe he should have straight up respond with his level of inexperience. And technically, one can imagine how to play out that out in a believable manner while maintaining a believable attraction. But the one plausible manner I can imagine also require a rock solid level of confidence in revealing that. Else, it starts to approach wish fulfillment in human behavior.