My APC UPS is connected to my computer with a USB-A to rj45 cable. It is the most cursed cable I own, narrowly beating out the type-A to type-A usb2 cable I needed to buy to get a HTC vive to work. (I later "upgraded" to a type-c cable with A-to-C adapters on either end.)

IIRC, the Ethernet standard means ports should tolerate 5V, but I'm still spooked someone's going to use the cable thinking it's something else.

Not every cable. Not if you make the connector a closed standard that can't be used without ruinous licencing fees and keep a squad of patent attorneys on retainer. Thankfully USB is not one of those.