Probably closer to production we'll see more about the S model.I don't really see anything to do with a GLE 63S on the Mercedes-Benz website. They list a GLE 350 d, GLE 400 and GLE 450 AMG. And then there is the GLE 63 Coupe.
What year is your X6M? Seems like it would still be fairly new at this point.
And welcome to the forum!