Thanks for posting. Would you mind sharing the capabilities that are reported by the device? Or feel free to PM me the “Doc ID” of the device in question.
Historically, SmartThings had a single Thermostat capability that combined all the features of various heating and cooling type devices around the world. In order to cover all the different features, it combined heating, cooling, modes, fans, etc.
Over time, they realized this didn’t work quite well as there’s lots of devices that are Heating Only or Cooling Only, so they broke things out into individual capabilities Thermostat Heating Setpoint, Thermostat Cooling Setpoint, Thermostat Mode, etc.
So if a Thing reports either just the single Thermostat capability or reports both Heating and Cooling capabilities, you get a Double Height Thermostat layout as mentioned in the post you originally replied to.
If the device reports that is has the Thermostat Fan Mode capability or the setThermostatFanMode() command, then the fan modes show up in the thermostat modal / popup. Otherwise they don’t.