Pretty sure it will be the same with Rebirth because : none of the dates contradict the others.
And that's the whole point. You can make the choice you want with the max affinity you want... You'll have to follow Cloud will. If he doesn't want to kiss someone, he won't.
Things is, the ultimanias are rarely a canonicity walkthrough, although people love using them as such. Usually its people going "THERE IS A SCREENSHOT OF THIS SCENE THEREFORE THAT SCENE HAPPENED, END OF DISCUSSION!!!!!" when really that's not how these things are intended I think.
I'd like some sort of clarification about how we should read the dates but my guess is that nothing will be mentioned that really touches on "what actually happened", more generic mechanical crap like "who shows up for the date depends on your affection rating", which essentially completely ignores what "actually" happened, or how we should interpret the effects of the events of the date on the feelings and continuation of the story.
And honestly, does it even matter?
Ultimately it comes down to whats been said before, with what we've seen concerning Cloud being aware of Zacks fondness for Aerith, and all the baggage that comes with Zacks sacrifice and attempts to get back to her, along with what has already been established concerning Tifa and Zack, I don't feel like there is any way to write a version of Clerith where it becomes impossible to do runs that do not make Cloud and Aerith seem absolutely godawful, and that's a problem.
Like I've said before, all runs need to make sense. Which means that whenever you write the continuation for the story you need to write it as fitting every potential previous playthrough. For Cloti, not a problem, in an Aerith playthrough we still get Cloud and Tifas growing romance as well as how much Aerith pines over Zack. Cloud and Aerith holding hands has zero impact on how we view them as people when Cloud "switches" to Tifa post Aeriths death, nor to Aeriths reunion with Zack post death.
We understand that it's fine to move on 5 years after someone dies. We understand that Aerith and Cloud was barely romantic, if at all, and that Tifa was already equally if not more romantically entangled with Cloud even before Aeriths death, we understand that Cloud can move on after Aeriths death, we understand that Aerith saw Zack in Cloud, we understand that Cloud was not himself.
Not a single route you currently play makes it so that "switching from Aerith to Tifa" makes the characters look bad. If anything the worst people look is when its still "Cloud and Aerith", since it still feels dirty to Tifa and Zack, but there are extenuating circumstances, so ok.
But what about a Tifa playthrough that (and this is even assuming player choice) switches to an Aerith playthrough in part 3? Now we would have a game where Cloud kisses Tifa, and then completely abandons her. And one where Cloud is constantly contrasted with Zack, with Zack looking like a perfect and loyal partner, while Cloud is dismissive of Aerith and kissing other women. And yet Aerith ignores that her best friend had kissed Cloud, and all the other baggage that we've mentioned about Zack sacrificing himself so that Cloud could reject the girl he kissed to be with the girl Zack was trying to get back to.
These people are awful, canonicity be damned. Someone could say "well, the Tifa kiss didn't really happen canonically so he's not really cheating" but screw that, if it happens in my playthrough, then it happens, that's the story I get to see, and that story is awful!
SE, if they have any sense, can't make a game where it's possible to play the characters that awfully, to have a story that twisted, and so they wont. Because ultimately the only reason it matters which date is canon is because we're trying to figure out "what happened" so that we can know what the backstory is that will determine what happens next, because that's what its all about, what happens next. But it doesn't matter what is canon for "what happens next", because "what happens next", has to fit all of them.
