Bandwidth is part of the profiling right? They targeted 300 GB/s from profiling and delivered 326 GB/s. They did target 4K.In my opinion, the X highlighted very well how Sony decided to make compromises on bandwith to keep the cost of the PS4Pro low.
I don't think that the difference is the result of any specific optimization made by MS.
PS4 Pro is built around CBR technologies to hit 4K