I would also really appreciate a reply from TP-Link

@IrvSp that is all nice, but apparently my router model is mentioned in the first message. So the question is still there. Is this how Smart Connect function supposed to work. I would prefer a Yes or...

But I am still wondering if SmartConnect is designed that way when a phone one-two rooms away from the router would loose wifi signal for a while and then reconnect. Because I though that switching...

@IrvSp thanks for your suggestion! I've tried turning SmartConnect off (now I have two different SSID - for 2.4 GHz and 5GHz). Phones still seem to reconnect from 2.4 to 5 and back once in a while....

@IrvSp SmartConnect is enabled. And when it is enabled there are a single SSID for both 2.5 and 5 GHz

I've also noticed that devices that are close to router (~3m) maintain their sessions for hours and hours, while devices in the other room reconnect once in 20-40 min.