WiFi can be frustrating. There is so much 'overhead' in WiFi compared to Ethernet (wired) that devices are really lucky to achieve speeds above 500MB. Plus there are many factors which influence WiFi throughput.
There is an enormous difference in the signal strength between WiFi access points and battery powered devices (smartphones, tablets)
- WiFi Access Points which typically broadcast at the maximum power allowed by the country regulations. In the US, that would be an EIRP of 36dBm - 4 watts (See, for example: https://afar.net/tutorials/fcc-rules/ There are dozens of web sites explaining WiFi power levels. That's just the first one I hit upon.)
- Battery Powered devices cannot possibly achieve the same transmit power. My Sony Xperia XZ2 Compact sitting four feet from the Orbi router reports a Receive Link Speed of 780 Mbps and a Transmit Link Speed of 468. As I sit here staring intently at the phone, those values change over time.
WiFi is entirely different from Ethernet. Every radio on a frequency shares transmit time. When any radio is transmitting, every other radio must wait for the channel to become free. During one specific Speed Test there may be not much "going on" on the 5G channel. The next test, there could be more devices using the network.
This situation does not seem unusual to me, and there are no parameters which would make a significant difference.
