Pitcher A and Pitcher B are the same pitcher. Do you see that? They have the same stuff. In one scenario, the pitcher is pitching in a smarter way, and it results in more wins. There are many factors that goes into W-L record, so obviously I'm not going to assume that anyone who wins 20 games is better in high leverage situations. But someone who does pitch better in those situations will win more games, possibly without a noticeable difference in other statistics.
Remember Tebowmania last year? Kyle Orton started the season and the team was bad. Everybody played poorly, including the defense. Tebow took over, and even though he was not a good QB, the team won games. The running game was better, the defense was better...there was something about Tebow playing that seemed to result in more wins. Maybe it was leadership? I don't know. But he won games.
If a pitcher accumulates wins, maybe its because he pitches well in high leverage situations. Maybe it isn't. I don't think Jack Morris should be in the Hall of Fame. I know you posted research, but I did my own research in the past. Morris has nearly the exact same numbers regardless of the situation. He is Pitcher A. But, he won games at a higher rate than most would expect. Why? Could it be that Morris has a reputation as a bulldog, a grinder, and the offense is more confident, goes to bat (literally and figuratively) for him, plays great defense behind him, is more confident with him playing? There's obviously something more - his teams weren't always so fantastic that it would justify that winning percentage when his ERA+ was so ordinary.
A pitcher goes and takes the mound with the goal to win the game. He feels he accomplishes his goal when he wins, not when he allows 2 runs over 8 innings. So W-L record means SOMETHING. It's part of the story.