fullylobsted, there is really no absolute memory frequency. The MB and memory vendors test their products and publist lists. The user goes from there using experience and opinion from others. I have a 2990WX - specifications:
MSI X399 Creation, Threadripper 2990WX, 3xSamsung SSD 970 EVO RAID0, 4xSSD 960 EVO on MSI AeroXpander RAID10, 1TB & 500 GB WD Black, G.SKILL Flare X F4-3200C14Q-32GFX, Windows 10 x64 Pro, EnerMax-MaxTytan-EDT1250EWT, Enermx Liqtech TR4 280 CPU Cooler, Radeon RX580, Aquantia 10 GbpS Ethernet NIC, UEFI E7B92AMS.120, AGESA SummitPI-SP3r2-1.1.0.2.
I think the secret to running 3200 MHz is the Samsung B-Dies chips on the memory sticks and I recommend them. I suspect you can run faster than this but it will take some tuning. If you are interested, I suggest you find a OCing forum and ask for help. Enjoy, John.
EDIT: Please read comments by goldenblaster at the bottom of this thread.