Not sure where you peeps got the "at Zen 3 IPC levels" bit that sounds completely made up by this article and isn't supported by any reasonable speculation either. The leak simply states Zen4D is a variation on Zen4 architecture, with clocks that focus on best clock/power ratios, slightly less cache and that it'll likely keep SMT (unlike Intel's small cores), as speculation that IT MIGHT not have AVX512, like regular Zen4 has (tho this might create problems like ADL has IMHO).
It says nothing about IPC and the only thing that can be speculated is that cache-sensitive workloads may contribute to it having slightly less IPC than regular Zen4 cores. But considering these supposedly comes a bit after Zen4/Raphael/Genoa, we don't really know how Zen4D is similar to regular Zen4 cores, maybe they're more aching to a Zen4+ design for all we know, maybe not.
Maybe don't add your own stuff that isn't in the supposed leak itself next time.