I wonder if this was spurred on by the fact that 360 backwards compatibility hamstrung their ability to profit from a lazy port of RDR being sold at a full $60 on other platforms. Best just remove people’s ability to buy anything from that generation in case it happens again.
Backward-compatible Xbox 360 games will still be available for purchase on the Xbox One and Xbox Series X|S stores, Microsoft says.
So no, presumably Microsoft just doesn’t want to deal with the tangle of close to 20-year-old code that holds up the Xbox 360’s store interfaces.