MacRumors, please correct your lack of physics knowledge. All electromagnetic radiation travels at the same speed in any given medium. To say that mmWave is faster or slower is simply incorrect. Higher frequencies can hold more information, but they don't travel faster.
mmWave is a set of 5G frequencies that promise ultra-fast speeds at short distances, ideal for dense urban areas. By comparison, sub-6GHz 5G is generally slower than mmWave, but the signals travel further, better serving suburban and rural areas.