I think the confusion comes from the spectrum of Editing-Revise-Rewrite. There are no distinct lines between the three nowadays, but a genuine 'rewrite' should be avoided unless absolutely necessary.

Heinlein's perspective is a bit skewed, perhaps, because of how prolific he was; while very few of his books sold incredibly well, the volume ensured that he could make a living doing it. His rules tend more towards the volume side than the quality side, but hey, volume is practice and with practice comes quality.