Positive Toe Angle On Diff Housing

Over the years people had mentioned that the factory built negative toe angle into the rear to help it tract better,same way they do the front wheels,none of those people worked for a manufacturer as a tech or engineer so I always questioned the theory,thinking about narrowing a diff and if I do I"ll point them straight forward. Thanks for the input.

I think that's just an "old wives tale", like so many things that people repeat.