As per comment by AMD and people familiar with the matter
(e.g. the stilt), there is a "memory hole" (memclk "hole") with the IMC hardware in a certain amount of Ryzen die samples.
The "hole" is typically located over 3200MHz but at least
the stilt who's been in close contact with got confirmation some chips have "holes" beginning lower than 3200MHz. Its another variable you'd have to consider aside from BIOS maturity, board and RAM sample.
Those that require workaround to attempt 3200+, AMD_Robert mentions tweaking
CLDO_VDDP. Its also mentioned by other insiders.
2933MHz at decent timings is still the best low hanging fruit to go for.