Just in case there's anyone who actually believes the Sinnoh soundtrack means something, it doesn't. It's just a track from movie 17 (Diancie), any soundtrack that was available for XY can be used in SM as well. The track was also heard in XY, but only once (Hawlucha beating Mega Absol), the reason it was used so rarely is because the version used in the movie only fits very specific scenes, namely ones that are meant to be short, like the Absol KO or the quick start of Pikachu VS Hariyama before the episode hit the commercial break (in the movie it played in the introduction, where we just see a glimpse of Diantha VS Wikstrom, so yeah it just kinda fades out). They do not have a full length version of the song that they could use for proper hype moments included in the SM soundtrack. If we ever do end up hearing a proper version, then you can speculate about DP remakes lol.
And when I say available I don't mean they literally can't use older music, they just clearly aren't going to, starting from BW they've had this trend of only using music from a specific pool (movie music that wasn't used in the previous series yet, in XY's case remixed versions of BW tracks, and in SM's case straight up XY tracks) probably for the sake of convenience. It'd obviously take more time to choose from 20 years' worth of music than just 3 or so. Though it could also be so that each series would have a stronger sense of identity, which would align with the lesser continuity in the story itself (which also started in BW so yeah).