You are thinking of big CPU clocks, this is not the speed of a single transistor switching, it is determined by whatever was accepted as the longest path of components for electricity to propagate through (think of a ripple adder as a simple example). You can have a much smaller separate clock and thus higher frequency for single purpose silicon when the path is significantly shorter.

60GHz here is talking about signal, you only need to create an oscillation at 60GHz not do fp multiply. There are various ways of doing so, but consider that it only takes three inverters to create a ring oscillator. As for the data - you don't need to fill the buffer at the speed which bits are sent, which is how you can interface with a lower frequency microcontroller, i.e the buffer is filled at a lower frequency but in large chunks i.e words.

Someone with proper EE and signal processing knowledge will explain more accurately but that's the crude idea (components frequency vs clock).