Sure, but Windows on ARM has to run on many ARM processors, not a specific one designed by MS. They could detect if the processor has non-standard TSO support and use that when running an x86 app, but they still have to do something to run the x86 app on a standard ARM processor.
(on ARMv8.0 where you don’t have those, barriers are used more)
TSO pessimization is the only way to make the thing work at a translation time cost that isn’t too high.