It wouldn't, and it's absolutely idiotic for some to suggest such.
Many years ago, my wife's FXT suffered from a high AF Learning A value. It was a tear in the intake boot after the MAF. You don't necessarily need to have a vac leak or an exhaust leak.
Our issue was solely because the intake boot would pull open slightly at idle, but once the engine torqued over slightly from being out in gear or driven, it would seal the leak and show no other signs of a problem.