[Gran Turismo]

I didn't check it in my car, but could well imagine that the AC system is deliberately designed so that the "Auto" setting is not able to automatically engage/disengage the "snowflake": This way, owners caring about fuel efficiency or who are sensitive to any cold AC may attempt to achieve the desired temperature in Auto mode without the compressor/snowflake engaged (as long as the outside temperatures would allow it).

Personally I'm leaving the "snowflake" always on, especially because the AC then always also acts as dehumidifier.