Think single-side/no layer PC boards from the 60's thru the early 80's..
Wrong again. Note where he stated "specially mounted".
I can guarantee you that your 60s examples were elevated OFF the circuit board itself. That IS a "special" mounting case, and is NOT the standard.
So, like he said, there has NEVER been a case where an engineer with any brains ever mounted a power element in proximity to a material subject to damage from heat, as circuit boards are.
Even a half watt device should be elevated to provide space between itself (the heat source) and the support substrate for its mounting nodes (circuit board pads, vias, etc.. Sometimes, even the mounting nodes need to be bolstered in one way or another to sink heat better.