DC controller question, temp seems high

[Damn True]

The "run it hotter" thing is something that came out of smog testing. If you had a motor that was slighty modified, or a bit long in the tooth BUT you were still subject to smog check the tip was to block off a portion of the radiator and/or install a really high-temp t-stat for the test. Get the motor hotter and the HC output would be lower. Not a way to run the car on a normal basis, but a way to skirt the smog inspectors (before they had all the high-zoot equipment they have now). Sounds like your mech may have been taught that at some point.