I made the conscious decision to not follow the thermostat standard for Auto mode as it would have required emulating a lot of the automatic function of the A/C and is not how split systems really work.
The “Air-Conditioner” ST device type is a much better fit as it supports Dry and Fan modes but I’m not sure if it is available yet and will also break any compatibility with thermostat-based automations anyway.
In Smartthings, Auto mode will essentially set lower and upper temperature limits, and attempt to either cool or heat to remain within that zone.
For Auto mode, the Daikin A/C expects input of just a single temperature and it will will cool or heat to keep it exactly at the degrees (-/+ ~1c). So unfortunately having auto mode as per the ST specifications doesn’t work very well as the Daikin A/C will only accept a “target” temperature and does not know the concept of cool/heat set-points.
As your outside temperature is so low, could you try just using heat mode and setting it to your desired temperature? As it is unlikely cool would ever come in to play