I can understand MC here. If he assumes things wrong, his relationship, that he just got back after years, would be gone. He is not popular while she is. And she stopped talking with him out of nowhere (from his perspective) and suddenly started talking again. Ignoring that he should be confused, he would also be walking on a thin ice, not knowing what is good thing to say.
Especially when all she did was write "Love?".
I am with MC here.