No, it is IMPLICIT that the first kiss happened before he left because he blames Katie for threatening to reveal it as a reason why he left, and their various conversations about it go back to before he kisses Katie in Ch 4.Katie was teasing them, but they never kissed until his return. Katie was jealous of the relationship between Leia and Will. She threatened to expose him, was kidding (according to her). Nowhere in that dialogue you quoted could I see any mention of a kiss between Katie and Will.