The block heaters on Thetas (and an increasing number of Kia's engines) are a 'dry type'. In the old days of steel blocks the best way to get a block warmed was to heat the coolant, as it has a better rate of heat transfer than the steel does. I can't recall if it's conduction/convection/whatever... steel sucks at it and coolant is better.
Enter the days of aluminum! This magical metal conducts heat WAY better than steel so it's far more effective to heat the aluminum directly and save time. Our block heaters for a V6 were 400W, now a heater for a 3.5 LambdaII is 250W. Less power, as effective (if not better) means less carbon footprint, tree huggers adopt pandas and every one wins.
Best part is no coolant system intrusion means a black heater in a Forte can be installed with considerably less mess, tools, or time.
But if my boss asks, it still takes me a long time... and our rate should NOT be reduced for it, at all. Thanks.