From my observations this approach seems to be somewhat sensitive to overall RAM latency/throughput - the quad channel w/ higher than mainstream frequency RAM and tuned timing on my setup seems to help a bit to offset it versus other platforms of the era which used dual channel but other wise perform the same or better overall - possibly ties into the above with Ryzen memory as well.
There are some advantages to doing it this way though it can hinder performance on older CPUs.
There is just so many areas we still don't have much data on. I clearly remember there was a couple small reviewers who tested 16gb vs 32gb on the 2080ti and 2 DIMM vs 4 DIMM and found consistently that 32gb and 4 DIMM kits offered 10% higher performance in minimum frame rates, and thats the particular area where CPU performance and driver overhead would be a problem. I wonder if we repeat those tests on a 3090 what the outcome would be?