Most? Is there proof for this? 3800MHz, sure, but 3733 seems quite achievable, but it does seems to require the right motherboard, UEFI and AGESA as well.
Most Ryzen 3k CPUs run with memory at 3600 but not even all. A big part will make 3733. Not so many will make a fully stable 3800. The same is with higher frequency. Most will make 4600, big part 4800, not many 5000 or higher.
If you check various results around the web then you can compare what users called stable and what they called benchable. Most results are not fully stable but users have something to brag about.
For me, out of maybe ~20 tested chips only 3 were fully stable at 3800 while maybe 3 couldn't run at 3733 stable. Still, all were 100% stable at 3600 with various density memory IC.
There is another factor. A higher capacity causes the max clock to drop on many chips. For example, my 3900X runs stable at 3800 with a 2x8GB kit, up to 3733 with 2x16GB and up to 3600 with 2x32GB at 1:1 IF.
Re reviewed memory kit. There can be found cheaper Samsung B kits that will run about the same. In games or most other things it really doesn't matter if memory has CL14 or CL16 so can pick 3600 CL16-18-18/16-19-19 Hynix kit which will perform ~0-1% worse in games but will cost half the price.
As far as the tested memory kit has great specs then out of competitive benchmarking it seems pointless.
I wish a higher capacity Xtreem ARGB as I see there are only 2x8GB kits and everything but the reviewed kit is on not the best Hynix IC. If they give a nice looking RGB then could also offer something at more popular recently 2x16GB. Probably it will be added in time.
Those sticks should be capable of pushing 4800+ on either platform.
I had a problem stabilizing Samsung B on Ryzen 3k above 4666 using kits that could run stable on Intel at 4900 ( max boot ~4800 on AMD, 5266+ on Intel). I can stabilize Hynix or Micron at 5000 on AMD without big problems but not Samsung.
If new chips will scale well above ~4600 then Micron/Hynix can be a better option, even for benchmarking but right now depends on the test it's or ~3800 1:1 at really tight timings, or something like 4266 CL13/14 or ~5000 CL18 and tight subs on some cherry-picked Hynix kits.
Interesting, I would assume that if the RAM is rated (XMP/DOCP) at DDR4-3733 (or even manually pushed up like what Nate did in the overclocking section), if you set that in the UEFI/BIOS to use that profile it should also set the IF clock to 1866 too, matching it 1:1. Is this not the case?
Many motherboards will set 1:2 IF ratio when you set memory at more than 3600. Some motherboards will boot at 1:1 up to 3800 but not many. Then you have to set the IF ratio manually.
AMD recommends DDR4-3733 (CL17) as being the sweet-spot for the lowest latency:
View attachment 152266
As I remember, just after the premiere, AMD was recommending DDR4-3600 as an optimal memory clock. I haven't heard about 3733 (even though it's on the graph) and I guess it's because they won't guarantee stability while pretty much every Ryzen 3k will make 3600. Still max guaranteed memory clock is 3200.