on the subject of Xehanort appearing multiple times beyond the 'Xehanort Saga', here's where I land. It's fine for him to continue to make appearances if there's a good reason for it, but it is kind of shitty that the final boss of vanilla KH3 isn't the last time he's fought. He appears as a mandatory story boss a whopping THREE TIMES after the initial KH3 playthrough. Once in ReMind, once in Limit Cut (which is mandatory for story progression) and at the end of MelMem. That's fucking crazy and takes away from Xehanort's 'finale' in KH3 so badly.
In the case of Melody of Memory, I just don't get why they felt the need to do it again... It DOES give this feeling of "huh?? I thought the Xehanort saga was over, why are we seeing him talking and fighting in an antagonistic capacity rn?" I'm so down to see the Nort man used in new, interesting ways, but this felt like a weird indulgence on Nomura's part.