Looking at that diagram it looks like the chipsets are what allow the overclock. X370 has overclocking enabled and dual X16 lanes. This will be your X99 board. Then there's the B350 that has overclocking (though with less lanes it seems, maybe the lanes are on the chipset not the CPUs?) And then your boggy standard A320 which is probably those turds we saw last week (the Gigabyte ones with no VRM cooling and crap VRMs etc).
AMD stopped rationing overclocks (though this did cause problems with boards that really weren't compatible) but only because they had to. With weaker CPUs you absolutely must enable overclocking or people would go elsewhere.
That will probably change if Zen is any good though. Intel have been charging for air for years.