The rule is - if it's going inside the wall, only a licenced electrician can do it. Yes it also extends to things like speaker or HDMI cables. It's mad.
I can understand requiring a license for any power wires behind walls.
I could also see the possibility that it's just an old law that doesn't consider data-only cables which don't have the safety issues that wires carrying power do.
While HDMI can provide a tiny bit of power and there are active cables for signal boosting, HDMI was never meant for power delivery. You might be mixing it with HDMI with Ethetnet.
It's definitely an old law that never took data cables into account, but the current interpretation is that any cable that carries electrical current has to be installed and certified by an electrician.
Yeah, it's all fun and games until you're at Macca's and someone says, "Oi, can you pass me a chippy?" and they get real confused when you go find a carpenter.
When I moved into a new house in Australia I asked the real estate agent if I could extend the fence, and he said I'd need a cheapie to do that.
I said ok but scratched my head as to why it needs to be cheap, only to find out later what he actually said was chippy, slang for a carpenter.