Slower WiFi speeds on cell phone than on computer using AX3000

Assuming "in the same room" means within 6-8 ft. of the Orbi router, these results appear lower than expected.  The iPhone 11 is capable of WiFi6:

(2x2 MIMO means the iPhone has two antennas)  This leads to a theoretical "Link Rate" of about 1.2Gbps.  It is common for WiFi devices to achieve about half the Link Rate in actual transmission.  Thus, one would expect with a Gigabit internet connection that the iPhone would achieve over 400Mbps in Ookla Speed Test.  (My ancient WiFi5 Android phone measures over 350Mbps when connected to my 2016 WiFi5 Orbi RBR50. This is with an ISP connection of about 350Mbps.)

So what could be causing the low speed?

• It might be the iPhone. Perhaps one of the antennas is not connected?  Since phones are portable, it would be (relatively) easy to connect the phone to a different WiFi system and perform a speed test.
• Is the ax feature turned on? (default is "on")  This can be found on the Orbi web interface, Wireless menu (at the top). There are options to enable/disable ax on the 2.4G and 5G WiFi bands. (alas, there are devices which are not only do not support ax, but simply will not function if ax is enabled on the WiFi network.)  The default is to enable ax unless one of those specific devices is on the network (and the customer does not want to get rid of it - or cannot easily remove it, like a thermostat).
• Is the iPhone connecting at 5G?  (This will show up on the iPhone Network settings and on the Orbi 'app' Device Manager.