Bob, all I got out of that article was that in "worst case" THREE conductors in a cable or raceway would never reach 60c under the load in 310.16 (25a for #12), presumably even if it was buried in thermal insulation. From personal experience I say it is a lot less for 2 current carrying #12 conductors in Romex with a standard dryer load (22-23a).
It never even got warm after my wife did several loads of clothes.
