But you need to know "the rest of the story," as the radio comentator use to say.

Back then almost all gasoline engines used carburetors, not electronic-controlled fuel injection. As a result, at idle speeds with a cold engine and the choke on, you would get a "washing" effect from the overly rich mixture of gasoline on the cylinder walls.

Obviously, that is no longer a concern with today's precise fuel injection.

So whatever the recommendation was back then, it really has no relevance to today's engines, one way or the other.

I agree that washing down cylinder walls was a risk back then.

However, a number of SAE and other technical papers that documented the effects of engine and oil temperature on engine wear using test engines (with no fuel wash effect) were being published in the 1960 - 1962 time frame. They were strictly focused on how much wear happens with a cold engine vs a warm engine (more) and whether it was better to warm the engine with no load (which took an extended amount of time) or whether it was better to apply a moderate load (with moderate revs) so as to reduce the duration of the warm up cycle. They found that it was better to apply load as soon as the engine had oil pressure, and that the time effects (extended time at cold engine temperatures) were more damaging than the load effects.

So obviously fuel wash could make it worse, but the 'drive it immediately' recommendation would apply to fuel injected engines as well. And diesels.