Hydroforming is a metalforming technique, nothing more. It's just like stamping, extruding, vacuum casting, forging, etc., but yet people see the term "hydroform" and they think it's some new spectacular platform design. Smart unibody design uses whatever technique is "best" for forming the various parts, and there's a lot more going on than just hydroforming or stamping.

Don't go rewriting history just yet - I may not have been 100% correct in saying that the first-gen Aurora used hydroformed rails (it did use a hydroformed engine cradle and dashboard beam, but a few minutes of online research failed to turn up any clues on the construction method of the rails). Regardless of how they were made, the first-gen Auroras were extremely robust platforms, and possibly the first GM FWD that was truely world-class.