This is disgusting practice. No way would a company such as Apple produce overpriced products with these flaws and class them as it being normal. It's not normal.

This is Apple, doing shady things once again and they're digging a deeper grave.

It's a feature.

How stupid do they think their customers are?

Also these certainly do not look like hot molded aluminum products. They look CNC wet milled (active coolant is sprayed all over the object). No reason for these to get hot enough warp in a wet mill. 

These are most likely warped in the manufacturing process of fitting the body to glass panel.

Still, "how" is less important than why are they selling these like this.

This is fun, "pre-bending" should be worse than the first bendgate?