I agree, he
IS very observant, smart and pays attention. In many of the cases when something happens between Sophia & Dylan, he doesn't do it or get it by being opportunistic. He always asks first, listens, plans and then does something nice for Sophia in hopes whatever he gets or Sophia is willing to do is by earning it.
The being able to watch Sophia getting dressed, he washed the dishes,
see her in a bikini by cleaning his room and keep it clean, then,
The foot massage, first he searched on youtube how to give a proper foot massage, then gave it to Sophia as pleasurable as possible making her relax, moan and de-stress herself with it, making it by merit to watch her change in the fitting room and to have fun for
both of them while at it.
The topless event, he made a deal and promises to earn it.
The bikini fashion event, to have more fun like in the fitting room, the foot massage and before that proposal, he already knew Sophia's bikini size by looking at her bikini before going to the bathtub.
The third bikini, to see her almost topless again even when they agreed it was a one-time thing but trying to find a way to happen again.
The Change clothes together but to earn it and make a pleasant moment, first he made breakfast in bed a lot earlier before Sophia would even wake up. Dylan is not a retard and he is neither selfish towards Sophia, to him, Sophia's happiness comes first, then in second what he would like to have with her.
Now, who knows what he'll do with the knowledge Sophia shared with him regarding her lingerie taste, maybe nothing or maybe something but what? how? and when?...