This is where people get confused.
There are 2 different things. You have the wires that ethernat runs on. This are a cable with 4 pair of wires that meet some standard like cat5e or cat6 etc. Then you have a method of encoding data into packets. This is ethernet. Many years ago they used to run a protocol call token ring over the same physical cables.
The USB extender things run some other data protocol over the same wires they are not actually running ethernet. Powerline networks take ethernet packets on the same 4 pair wire convert the data to some special data protocol that runs over electical wires and then convert it back to ethernet on the far side. The powerline units do not have the ability to convert the...