You're meta gaming. At this point Barret, Tifa, and Cloud have 0 fucking idea that Aerith will eventually be killed by Sephiroth. The RGB Barret, Tifa, and Cloud standins defending the future that they fought for makes complete sense, and they likewise have 0 way to know that this Barret, Tifa, and Cloud could potentially save Aerith's life because the only future they know and can know is the one where she already died.
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