When the other team is equally good with similar talent, I can buy your argument. When you’re losing close games to teams that aren’t very good or have less talent, that’s not luck, it’s coaching. Most games with a disparity of talent aren’t close at the end, so your statistics only tell part of the story.
I agree that what happens in the other 38 minutes is more important than what happens in the last two. What about when you are in games when you are up against teams that have more talent? Are you willing to give any coach credit for being in a close game against opponents with superior talent or do you only want to look at one side of the coin?