I think we have to accept that there are always going to be some limitations on our actions. Even in a pen & paper RPG with a living, breathing GM, if you flat out refuse to participate in the story he/she has prepared, the game is eventually going to break apart at the seams. It's a question of degree: when the game offers your character a choice, there's a big difference between it having no plan whatsoever for the less likely choice and not having one specific option the player really wants.
I think DPC does a much better job than most handling choices though it's definitely not perfect; the resolution to the Maya/Josy crisis in Episode 4 is the poster child not getting it right, IMHO. By comparison, I think dating Jill is handled very well. Sure, you may have preferred that the MC just ignore Jill entirely, but she's clearly an important part of the game and can't be sidelined completely.
The question is if you can express clear interest in Jill as a friend rather than a romantic partner, and I'd say you can. One extremely chaste playing tennis is about as non-committal as it gets. Even Jill will recognize that the MC just doesn't seem that into her, and is willing to accept that they're only going to be friends.
Now it's true that Jill will almost certainly take the news of the MC hooking up with Bella poorly even in that case. But that's because she has a huge crush on him, and that's not something even the purest, noblest CHICK MC's could change. Again, what matters is that when we finally hit the breaking point, Jill's reaction to an MC who showed minimal interest in her has to be much calmer than her reaction to an MC who deliberately wooed her while pursuing Bella at the same time. I'll be shocked if that doesn't happen.
On the specific topic of asking Jill out, I'm going to have to disagree with you. The MC is a young boy, Jill is a pretty young girl, and Tybalt is a complete asshole. Even a CHICK MC who doesn't like Jill is going be bothered by Tybalt's attitude. It seems well within the MC's established personality to ask for a date rather than accept being humiliated. We are explicitly given the option to make the date about Tybalt rather than Jill, and the MC is under no obligation to make the date romantic. So at least to me, this feels like a successful implementation of choices in a computer game: the MC will take the mandated action, but we are allowed to choose WHY he does so and we can influence the eventual outcome of the that choice to match our stated motivations.
