I used the thermostat example because that's the one everyone is familiar with, but if that's all it was then you'd be right, temp readings would vacillate around a set point. But Porsche doesn't use a thermostat. That would be like using motor mounts. And as we all know Porsche doesn't use motor mounts, they use magnetorheological fluid-filled computer controlled engine damping units. For cooling they use a map-controlled thermal cooling management system, which is still a mouthful, but a lot easier to pronounce than magnetorheological, even in the original German.

Anyway, it does work, and in the real world. The number displayed is not arbitrary. It is, like all the others, an actual live reading of the cars real-world status.

 

^^^ The system works so well that the temp does not vary?