They're not. This kind of projected-electrode plug was originally designed for AMC and Chrysler in the late '70s when they were trying to make engines run reliably with extremely lean and stratified charges—and they did a real nice job of that, so much so that Chrysler kept on using them well into the '90s on motors including the 4.0 Jeep Six and 3.5 V6. The extra-long electrodes put the spark point a lot closer to the center of the combustion chamber and moves it away from quenchout zone near the chamber walls, which in turn results in a reduced chance of misfire. They are of the same heat range as the stock Slant-6 plug.
