@JS_novice ? doesn't Deco have separate SSID for 2.4/5 and 6GHz? Even if it doesn't, You can create guest network for 6Ghz only and connect to it.

On phone remove 2.4/5 SSID and connect to 6GHz only, then it will not switch between SSIDs. Or unselect autoconnect for 2.4/5 SSID, then u may manually switch when needed.

  @JS_novice I think (maybe wrong) for MLO there is a separate SSID, so in my network with 2xBE65 in AP mode it's 4 SSID:

1) Host Network : for 2.4/5G devices. I keep 2.4G disabled so everyone forced to use faster 5G

2) Host Network(6G): for 6G devices, such as WiFi 6E and later, this one doesn't use MLO

3) MLO Network(5GHz & 6GHz): same as 2 but has MLO enabled, WiFi 7 devices with MLO support connect here and can use 5G&6G for better speeds

4) IoT Network: this one set to use 2.4G only for IoT devices which don't support 5G and WPA3

* MLO is WiFi 7 only thing, if client device supports it it should connect to MLO enabled SSID 3

** If some random client device without MLO WiFi 5/6/6E/... connects to MLO enabled SSID 3, I think it may or may not work or may work as You described above. If I were You I started to test MLO on separate SSID. No older (<WiFi 7 with MLO) devices should use MLO SSID or knowing TP Link it may be a lot of bugs if it will work at all...