WL1837MOD: How can I confirm DTIM operation?

Following up on https://e2e.ti.com/support/wireless-connectivity/wi-fi-group/wifi/f/wi-fi-forum/1227753/wl1837mod-can-power-save-be-configured-differently-using-wlconf 

I discovered that the wpa_supplicant supports configuring the DTIM period an Beacon Interval:

# Default value for DTIM period (if not overridden in network block)
#dtim_period=2

# Default value for Beacon interval (if not overridden in network block)
#beacon_int=100

If I inspect a nearby network and look at the Traffic Indication Map, I can see the DTIM period is set to 2 (and the Beacon Interval in the network list shows 102.4ms:

I have had success changing the beacon interval using the parameter in the supplicant configuration file, but I can't seem to inspect the Traffic Indication Map to determine whether my attempt to set the DTIM period to 1 was successful:

I assume this is supported, but how can I confirm the setting is having an impact?

I tried using "iw wlan0 link" and "iw p2p-wlan0-0 link" but the response is "Not connected"

Tom