Seems like RSEs are getting built on all trim levels - here's a '23 Yukon XL SLT w/ RSE -->
https://cws.gm.com/vs-cws/vehshop/v2/vehicle/windowsticker?vin=1GKS2GKD2PR104995&bac=119446
Your dealer is thinking about the '22 constraint on RSE that was at zero for most of that production year. It could still be on constraint, but they are at least building some of them.
What does seem to be on zero constraint is Max Tow and Pro Safety Plus packages. I can't find a single '23 model in transit that has those options. Also, looks like there's ~10 Duramax Yukon XLs in transit across the entire country. Not a zero constraint, but highly constrained nonetheless... This isn't looking good for my Yukon XL SLE w/ Max Tow, Pro Safety and Duramax order...