Surf SOHO w InControl - Min Client Signal Strength

I am having trouble with devices that move just far enough away from the AP to have throughput issues. I have a separate SSID for for 2.4 and 5 gHz radios but devices are persistent to the 5 gHz SSID when moving far enough away to not make the Min Client Signal Strength threshold of -80 Dbm.
Is this a bug or do I not understand how this works?