I have seen one, MS mentioned using less CPU cores on IO, however if MS are using CPU during IO thats still taking RAM bandwidth away from doing other things even if the CPU is only using half a core or whatever, so when doing IO you slow down other stuff thats waiting patiently and using up cycles.........
Ps5 has no CPU on IO other than initiating it (obviously), its all handled directly SSD to RAM, Ps5 GPU could be rendering other shit using the memory bandwidth while ps5 is pumping in new assets and not be interupted or stalled....
IS XSX IO efficient - hell yes it is infinetly better than PC even with INMe and >>>> this generation - but Ps5 is even more efficient.....so its not a critisism, both have spent their budgets where they believe will matter.
Its all about how many cycles you use up doing stuff in the time of a FRAME, and if those cycles stop other things from happening in parrallel then its sort of a bottleneck. But if Ps5 uses less cycles for some stuff, but XSX has more compute, maybe we will see similar .........end results
Anything that uses CPU that does not need to is wasting cycles both for CPU and the shared memory bandwidth / bus.
Then there are coherency and cache scrubbers, if you dont have them = more cycles. These are only the hints, we have heard of so far, there will be more and Cerny seems to have gone 100 % crazy on removing them, maybe it will all balance out vs more power approach (who would of guessed

)