By misleading, do you mean that the advertised 1200 Mbps cannot effectively be used?

That's part marketing and part principle due to Powerline itself. Data transmission over normal power cables is usually one of the most stupid ways to transmit data. Since power cables are not designed to transmit data, especially not at the speeds required today, the difference between gross and net is getting bigger and bigger.

https://de.wikipedia.org/wiki...

Since all types of data transmission (Ethernet, Wlan, LTE, etc) specify the transmission types in gross, it is not misleading to advertise Powerline with the theoretical gross speed of 1200 Mbps.

Another counter-example. How can it be that Swisscom advertises its Wlan Box 2 as being able to transmit 4800Mbps via Wlan? That is almost 5 times faster than via network cable. So why don't they just pull out all the cables and only do everything via wifi...?

Swisscom WLAN-Box 2 (4800Mbit/s, 300Mbit/s)