That's not stretch, that's the "rim guard" portion of the tire. Some manufacturers add an extra ridge of rubber on the sidewall (commonly called a rim guard) right above the face of the wheel to protect the wheel. In the event of hitting something with the side of the wheel that portion of the tire will take the brunt of the damage. It does flare the sidewall out a good bit which gives the appearance of more stretch than there is. Anywho, some stretch on the sidewall is good, it sharpens steering response.

 

The RE71RS got rim guards too, but clearly has more thread width also. both 295/30 are on the max recommended rim width (11")