I agree that those "AX9000" marketing numbers are fake.
>This obviously depends on your hardware and environment
This is the key point. If you have:
A high link rate client.
A high link rate access point.
Line of sight between the two, same room.
A low utilization and interference channel.
No one else heavily using your Wi-Fi.
Non-bad drivers for Wi-Fi.
Then TCP throughput of about 1/2 to 2/3 link rate is possible. 1200 Mbps link rate yields 600-700 Mbps speed tests. Some applications have small TCP windows so their throughput drops on 5 ms latency wireless versus <1 ms wired.
Yes if you plug you always get 920 Mbps throughput.