Let's do a quick rewind of Dylan's side of the things...
It had been perfect. Actually, too perfect that it even made Dylan feel like it was a dream. He might be naive when it came to feelings but he wasn't naive or inexperienced in kissing. He has had his fair share of 'fun' in life. And that's why it was very surprising to him that a mere kiss was making him feel all those feelings that he couldn't even describe in words.
But he could tell that the kiss was special because of her. Because it was Cali, he felt like he was back in his adolescence. He really felt like a teenager who was getting excited because his crush had the same feelings as he did. But the main point here was that Dylan actually had never gone through that feeling before.
His first and last real relationship wasn't the result of his flirting. It was the other way around. His ex was the one who came on to him rather than him doing it.
Oh, I feel bad for my baby Dylan right now. But at least, he has Xiu with him.