Then why has AMD said themselves that ST performance is only up by around 15%, it's obvious that the MT performance has a lot more to do with the increased power limits rather than ipc and the higher frequency is a result of that. The ST performance isn't tied to power limits which is why the gains are much more modest.
Don't even need to make assumption about MT and power limits, Robert Hallock has already stated in an interview recently that the increased power limits for Zen4 at the high end models was done simply to allow for higher all core clocks during multithreaded workloads - basically Zen4 is pre overclocked from the factory