Thanks for the link, it is an impressive article and while I work in IT, the electronic may be a bit off my league (I just solder a bit around IoT devices and flash them).
I realized with your comment that I have never actually tested the plugs when they are next to each other (say, on an extender). I did not expect there would be a physical limitation below the advertized 1Gbps (I now all I got 400 Mbps I think but I am not at home to get that with a local iperf loop). If they cannot deliver close to that I would be pissed off :)
I have, again from memory, a 2x1Gbps tplink pair.
This said, my power cabling is sub par so this was the obvious reason for me for the lower bandwidth.
200Mbps is their real PHY speed, 900Mbps is just a Scam