This is quite interesting.

My only thoughts are as follows:

The fan clutch will couple when the temp of the thermostatic spring in the clutch reaches about 100°C.

So, with the vehicle's temperature gauge at 105°C, you would think that the temp in proximity to the spring would be nearly 100°C. and the clutch would couple.

I'll get Dave to comment on the clutch. He's had them definitely working in the past. I'm fairly sure mine does not work, but, I'm not worried about it.