Wow. I knew I was gonna stir up some shit with that ending, but I had no idea I'd receive this level of backlash!
All I ask is that everyone reserve judgement until later in the series. Keep in mind, this is chapter 2 of a 7 chapter story. There are lots of things to be revealed in the coming chapters. I am not here to force anything down anyone's throat. I'm here to write a story. A story that has twists and turns, will play with your emotions and keep you guessing. How boring would it be if every story was the same? If every story followed the "rules" of that genre? I guess what I'm asking for is a little trust. Besides, we all have our kinks, me included!
The main issue is that reserving judgement doesn't do much once the incest has been identified as fake or as stepcest. Incest fans generally consider stepcest worse than being completely unrelated to each other, because it feels like a copout. It's the stupid workaround mainstream porn 'stories' use instead of just roleplaying full incest. You hadn't gotten a lot of that backlash yet, because it was very subtle, only really identified in a single line that could easily be edited out. Christmas Eve has all the hallmarks of a full-incest story, and it was generally assumed to be one. This one did at first as well, with the single 'step' line early in the game ineffectually intended to deflect Patreon's attentions, until the end of this update.
As everyone said, it recontextualizes the whole game in significantly negative directions, and it is particularly damaging to the assumptions about Heather's intentions.
If the intent of the stepcest story instead of full incest was to evade Patreon's rules, that will not work. If someone reports it to Patreon, they will come after you anyway. Step/adopted/foster relations don't matter to Patreon, they're all incest. That's why most Patreon-successful incest stories use "roommates", "landlords", "landladies", and "tenants".
If the intent is to cause drama and have an antagonist trying to take the kids away, a common tactic full-incest games use is for it to be the dead wife's parents who are trying to take the kids away from the widower husband MC. That preserves the dead wife as having only been with the MC, preserves the girls as actually being the MC's instead of being someone else's kids he's fucking, and just generally is a better structure for the story.
While we all have our kinks, this change loses incest fans for good. I've already dropped my support, as I'm sure you saw, and it already damages that trust you're asking for.
If there's something that would salvage the story for incest fans, or if there's some reason this recontextualization isn't as damaging as we're all taking it to be, I'd recommend talking about it now rather than waiting another several months for the next update. Once your game is completed (or even once the next update comes along, if it adds more explanation for these issues), there isn't any further reason to keep spoilers secret, and if you lose all your players and support while working on completing it, what benefit did maintaining those spoilers actually provide other than annoying some people for a few months?