Gl-mt3000 - 3rd wireless 5G antenna

is it used only for dfs detection or does it serve wifi as well ?

The Filogic 820 chip supports Xtra Range technology and adds a 5G antenna to improve WIFI service.In the actual FCC and CE certification process, we found that the third antenna also plays the function of detecting DFS signals.

Am I correct to say the gl-mt3000 is capable of 3rd guest wifi for 5g wifi ?

Nope. I think it more like strengthen the signal gain for both Tx& Rx . And what you feel is the distance and signal signal strength. not related to the guest wifi.