I think arguments in general around the loose canonicity of either Princess Rosa in the Loveless play, and the Gold Saucer dates themselves, is a dead end anyway.
The credits and datamined discoveries about the development that lines up with Ultimania statements etc. doesn’t alter the facts and again, the context, about these scenes.
Aerith as Princess Rosa and her Gold Saucer date being canon doesn’t suddenly alter the context. And it definitely doesn’t alter the context of the dream date in the church, low affinity or high affinity or not.
In fact all three, Aerith as Rosa, her Gold Saucer date, and the dream date, massively serve to reinforce the idea that this romance is one that isn’t meant to be. And not only that, but that it isn’t real, it’s a red herring, an illusion.
Aerith as Rosa, and Cloud as Alphreid, are merely acting out parts in a play. They aren’t even properly acting out on stage like in the OG. It’s a literal virtual alternate reality being projected.
And in this respect, I agree that it makes more sense for Aerith to be Rosa, because it furthers along the beats and themes in her story and in her dynamic with Cloud that as far as romance goes, it’s wrapped in illusion, “You can’t fall in love with me, even if you think you have, it’s not real.”
The dream date, another alternate reality, has Aerith almost seek to act out a play once again, “Just play along, ok?”. It’s not worth going into once again the multiple times the NPCs in this date, and by extension the writers, scream at the audience about how even when pretending or playing along, Aerith and Cloud don’t match as a couple. The church scene is where it’s made explicit that this buildup has been a red herring.
And her Gold Saucer date, canon or not, low affinity or high affinity or not, is Aerith seeking and failing to connect with the real Cloud. She reaches out first, and when Cloud tenderly questions her, she says “Just until the ride’s over.” Aerith wants in that moment something Cloud can’t give, and even in high affinity, he can only comfort her. The nature of romance is rich and varied, and Aerith and Cloud’s, beyond its role as a red herring in the wider narrative, is also one wrapped in tragedy. This is expressed in their date.
And it’s bookended in one of their goodbyes in the ending, the one that calls to mind Advent Children, where they stand back to back, and hold hands once more before Aerith fades away. Here it’s Aerith comforting Cloud.
So there is a lot to suggest the game is telling us that Aerith is Rosa, her Gold Saucer date is the one to be seen in order to understand their relationship, and make better sense the nature of the dream date scenes.
But canon or not they simply don’t change the characters, context, or story. Continuity and cohesion are important yes, but so is understanding what’s being shown in the first place. And understanding the narrative intent behind these scenes and why the developers and writers would want us to see them in the first place.
So any confirmation of canon for the role of Rosa or the Gold Saucer date isn’t, and wouldn’t, suddenly be a confirmation about anything more than the information being conveyed within them is important to see and understand.