'dual-rank modules continue to be a problem area for AMD'

[kalniel]

I was reading a useful memory speed with Zen 2 article at techpowerup when I saw the above quote in the conclusion page (https://www.techpowerup.com/review/amd-zen-2-memory-performance-scaling-benchmark/5.html)

The full sentence was:

Another demerit of choosing one 16 GB module over two 8 GB modules in dual channel would be that dual-rank modules continue to be a problem area for AMD

I'd not heard this before. Has anyone else? And are all 16gb modules dual-rank at the moment?