Speculation time...

[Hummer Guy]

Originally Posted by RazM

A couple of reasons. The final look of the HX was agreed upon far before a full size sculpt was ever worked on. This has absolutely no features from the HX at all. Another reason would be that if it was an early HX design, I doubt they would avoid discussing it.

Actually, that's not entirely correct. The HX has several early builds with different styling -- they were frames only with no engines. The vehicle pictured was one of those.