How do you support something that is unsupported?
You're missing the bigger picture. There's "supported" (technically works), versus "supported" (defined by ratified standards bodies, and produced by standards-compliant mfgs).
That's what I was pointing out in my description of how mobo mfg's list supported DRAM speeds. They list 4600 (*OC) as a "supported" DRAM clock speed, because their board was tested to support that clock speed in their labs. They list "supported" 3200 (no OC) DRAM clocks, because that is the highest standards-based DRAM specification that is mfg'ed today.
Also, don't confuse mobo DRAM "supported" speeds, with AMD's "supported" DRAM clock speeds. The two are not the same, although in the real world, generally, you can push to the higher mobo-supported speed, assuming that you don't have a CPU with a "dud" memory controller, and you buy (binned) XMP-rated DRAM of that faster clock speed.
Basically, there's officially standards-based "supported" DRAM, which is non-overclocked, strictly JEDEC-standard stuff, that the CPU and mobo supports. And then there's the overclocker market "support", for XMP DRAM and pushing the CPU's memory controller past it's "officially standard" limits (but generally doable, in practically all cases).
Think of it this way, it's kind of like rating a car's top speed. The car itself, can push 120MPH. But because there are no legal highway speed limits higher than 70MPH, they list 70MPH as the car's "official, standard" top speed. Get it?