Shinji's doing his best to keep a sharp look out for anything that could possibly help solve their immediate problem, but it's easy to get distracted by Kai's excitement.

And it's not like what he's saying is wrong, but it just seems like... a stretch, to think they'd just find some along the way? The way he says it so easily makes Shinji hesitate, but, "Um," he just has to ask, "Do you think there'd be more bugs here than normal?"