I think the article is poorly written. The lightweight panels and shortened weld flanges are undoubtedly across the entire line. The paragraph mentions both Eco and then later Cruze which I think creates the confusion.
The shortened weld flanges would require two sets of dies if the shortened flanges were used on the Eco only. The thinner metal is within the tolerance a set of dies could run so they may be Eco only although it makes little sense from a production standpoint.
Now, some of you guys would know, is this car manufactured solely in the U.S. or is there an overseas manufacturing facility too? In that case I could understand different tooling. There would be dies both here and there and differences between them would make sense. In other words, is the Eco version imported?
US Only for the US market, at Lordstown.