ERK told the story at the San Diego ComicCon of how Lovell once praised him for the composition of those particular illustrations, Jose. Ray said, 'yes, they were particularly good, weren't they?' Lovell was taken a bit aback by this apparent immodesty until Ray pointed out that he had lifted them wholesale from Lovell.
Kinstler never denied his swipes, nor was he ashamed of them. Just as artists like Rockwell and Leyendecker used photographic reference without shame, so Ray took from whatever was at hand. As you say, he was able to draw anything, just couldn't justify spending the time doing it for the money they paid him. His choice.
When he followed Kubert on Jesse James, he described what you and I saw as swipes as a 'collaboration' of sorts - "We were working on the series together and of course there was an overlap." And the biggest influence Kubert had on him was to get him to abandon the pen in favor of the brush for his comic work. It actually allowed him to stay in comics for five+ more years and to make a living at it by producing enough pages to survive on.
Peace, Jim (|:{>