It could have significance on the Sage route. It could have long term relevance on the Sage storyline. The routes have to diverge at some point.
It also could become a common plot element, just because the girls don’t see the MC if you’re on other routes doesn’t mean their actions won’t still happen. The girls clearly want to tell Chad and break them up. The scene where they see MC/Sage talking implies they’ve spoken about MC before. They’ve some vested interest in the Sage/Chad relationship and their entire motivation isn’t born of just seeing them together in that moment.
Theres more than one way to skin a cat. If DPC does want to make Mel/Sarah breaking Chad and Sage up a “canon” plot point shared across routes he can. Just because that is a scene isolated to Sages route doesn’t automatically make it irrelevant. The game makes a big deal about Bella letting you call her Bella... being able to call her Bella wasn’t part of the common “canon” before Ep5 because it only happened on her route. Come Ep5 the game finds another way and has Bella like you because you helped with Cathy.
Sage herself is brought back into the fold regardless of being fuck buddies. We obviously shouldn’t assume stuff seen on one routes is also true on other routes but to dismiss it entirely is also unfair because DPC has shown he will homogenise routes. There’s just no way of knowing what will and won’t stay on routes.
DPC has the power to make more or less anything happen, but that does not mean he can make it happen
well.
The problem is that Sage and the MC passionately kissing is a legitimately big deal to Chad (either because he does have genuine feelings for Sage buried deep down, or because letting such a public challenge go unanswered would undermine the useful fiction that he cares about Sage). It would be a very natural spark to ignite a new conflict between Chad and the MC... if it happens.
If DPC wants that conflict either way, he will need a backup spark that can start the conflict for non-Sage-path MCs, or suppliment the conflict for Sage-path MCs. But that creates a new problem. If the backup spark is a minor issue, it will make the subsequent conflict feel utterly overblown - much like the MC angrily storming out on Maya and Josy felt hollow when players had declined to interact with them much. On the other hand, if the backup spark IS a big deal, it will run the risk of overwhelming the original spark. Those on the Sage-path could feel that their connection with Sage is being trivialized, because the overall story won't have anything to do with their actual relationship.
In short, I think trying to force both paths through the same events risks satisfying neither side. Better to either unify the path leading up to those events, or customize the events for each path.
