Temp control for Pax on any aircraft is a bit of an art and needs to be moniterd and adjusted for the following circumstances
Are the Cabin crew doing a service, yes =slightly colder, at night the cabin crew request colder temps whilst they do the service because they get hot running around, but the temp must then be increased when the service is over and the pax are asleep.
Is it a daylight flight ?. pax dont sleep=slghtly colder
is the temp sensor next to a light, (dont laugh A300 actually had this problem), =slightly colder or manual control. (need feedback).
I too am amazed at how cold the cabin is regulated on some of these aircraft. many pax actually catch a cold during the flight. a comfortable night cabin sleep tempreture I was taught is 25-26 degrees (c). jeez guys warm it up a bit at the back after the service, and yes I am a Flight Engineer on classics