From the examples you have listed, the AMD board supports faster memory? So I am not sure why you are asking about Intel supporting faster memory. At any rate, it means nothing, except that is what these particular boards are "capable" of running at the time of their release.
It means you can buy memory that is RATED to run at any of these speeds.
The OC setting mentioned means that there probably is no memory made at the time the board was released that you could buy at that rated speed. So to achieve it, you technically must overclock a slower module to get there, either by bus speed or multiplier.