Maya/Josy and Jill are a lot more romantically involved compared to Sage and Bella at the point of the choice, going purely based off what the game shows and tells us
When you tell Sage she's initially reserved, almost apprehensive because she doesn't want to risk losing MC as a friend. It isn't until Episode 10 that she really begins to express her feelings. If you let her down, she says she's thought about dating Tremolo, but wasn't ready, so she's a bit disappointed (especially if you've been on her path from the very start), but doesn't hold it against him. To me this suggests that while there are feelings there on both sides, its not deep enough to break her heart.
When you tell Bella, she's quite clearly very reserved, Tremolo makes her happy, taught her how to breathe when she felt like she was drowning, but there are also many walls and "elephants in the room" that they need to address. She also doesn't hold it against Tremolo because they just aren't that involved yet.
Jill feels Tremolo is her destiny, and it's meant to be. To be on Jill's path you have to quite clearly show that she's your number 1 priority and throughout S1&2 you go to extreme lengths to stay on her path. It's obvious that at the point of the decision, she loves MC, and there are clear feelings there, there's no logical reason for a Tremolo who is on Jill's path, having chosen to fight for her and met her friends, to turn around say "I don't want to date anyone at the moment." Jill's path has one clear jumping off point, and one less obvious (the birthday date if you choose to look after Sage). The game gives you a choice.
Josy/Maya, I understand the frustration, I don't think it's particularly unreasonable for a person in a Throuple to turn around and say "this was nice, but it's not what i'm looking for, i don't enjoy the dynamic xyz". But again, there is quite clearly feelings involved, an established couple have let you into their relationship, Josy quite clearly loves Tremolo, ans while Maya is a lot more emotionally reserved, I think she does too. This path doesn't have any real jumping off points when you're on it, but you have to actively decide to be on the path.