@Joe-P Looks like you're confusing gross line bandwidth with actual net payload throughput. As with any other shared-media network (like WiFi), expected net throughput is about one third of gross bandwidth.

Where's the rest? You can't send and receive at the same time, so transmission "acknowledge" packets disrupt transmissions. You have media noise and random disruptions, packet loss and transmission retries and errors.

 I find this 213 Mbit/s speed too slow from a 1000 Mbit/s PowerLAN adapter. (I expect min. 300-400 Mbit/s)
My WiFi Intel Dual Band Wireless-AC 3168 reaches 324 Mbit/s and a Realtek 8814AE Wireless LAN 802.11ac reaches 490 Mbit/s.
I have to try a 2400 Mbit/s adapter from another manufacturer.
I'm disappointed.