> Am I understanding that this is doing something the chipset wasn’t designed to do?

Every WiFi modem has a testmode. It's required to verify the TX/RX chain during manufacturing and for compliance testing.

Seemingly you can read out the entire spectrum at full rate.

mega samples per second. IOW: sample rate.

The significance is that most off the shelf SDR platforms have much lower specs. Almost all of them use the same Analog Devices transceiver chip.

Msps = Mega samples per second