It's not USB-C. The same thing would happen with USB-A/B, or any other standard which provides power with a well-defined polarity. The mistake was in the simplest part of the standard: the pair of wires which carry the voltage reference (GND) and the main voltage (Vbus), a pair of wires which exist since the original USB standard, and in many many other standards (ever used a "PS/2" keyboard? guess what, two of the pins are GND and Vbus!).

As for cables fraying, the most common result is an open (an unconnected wire). If two of the wires get damaged at the same time, you might get a short (and the USB standard mandates that a short causes no damage to devices). But reversing a pair of wires? It's ridiculously unlikely that fray and tear on a cable not only severs a pair of wires, but also reconnects them backwards!