How do YEC Christians explain why "flawed" Carbon 14 dating nevertheless tends to agree with other dating.....?

Because they usually don't know anything. Most religious leaders do not have backgrounds in science. Or if they do, it's usually in a field like "engineering" or "political science". Then creationists flaunt at how they got an educated person to support their cause, even though that educated person still knows **** all about evolution and carbon dating.