Checking a few things over, I noticed that the radiator fan and the a/c condenser fan come on and go off together. This "didn't seem right" but looking at the circuit diagram, the relays are wired in parallel so it is working as designed.
Thinking through the implications:
1. If you run the A/C when the engine is cold, it may take longer for the engine to warm up - because the radiator fan is blowing unnecessarily (Although the thermostat may help)
2. Running the radiator fan unnecessarily might shorten its life
3. Also you are wasting some power through running the radiator fan when it's not needed
4. If some of the electrics controlling the radiator fan were to fail so that it didn't run when hot, turning on the A/C could be a good idea because it will probably make the radiator fan run.