It's a player's choice. Whether you will spend time with Summer or Beth should be up to the player. There's a reason why most if not all the popular games have it and don't get me wrong, I do like Visual Novels, but this game was clearly designed to not be one and it's obvious as soon as the second day starts; Rick tells you to go see him on his garage, it doesn't happen any time soon.
As for chronology, it's a matter of using multiple flags and variables throughout the game. Do you want a threesome with Summer and Beth? Well, you need to advance with both of them a certain amount of scenes. You are not a virgin anymore? It can be easily reflected with a single variable. It's not impossible, hell, it's not hard. I understand it's your personal choice because this is your port and you are not asking any money for it, but it isn't really an excuse, it just feels lazy, and that's not even starting with the UI. For a version with more content than the original, it does feel like a lesser product.
I'll just say what's the point of playing a fan game if not to explore your favorite world? This feels like an over-glorified image reel, and VNs are not supposed to be that. Can open-world get tedious? Sure, but the point is making it less tedious. I appreciate all the changes done in this port, and it does have some nice work on the sides with added dialogue and scenes, but not enough care was put in making it linear outside of some very tiny details, and I think that's simply because the storyline isn't made to be linear and tiny changes won't change that
Well, whatever, good luck.