Most of what I think these people were referring to was the Asians' tendency to copy things. And Hyundai's been good at copying other products.
The 2.4L 4 cyl in the 2000 Sonata is a purely Mitsubishi design, with Hyundai manufacturing under license from Mitsubishi. The transmission is a similar deal with Mitsubishi. The 2.7L v6 appears very similar to some Mitsubishi engines, but I don't believe it's Mitsubishi's design, per se.
As for the electronics, I believe the 2.4 used Mitsubishi while the 2.7 used Bosch. In either event, Hyundai did what's called reverse engineering. They took a computer system that had already been designed for fuel and transmission management and built the system around it, while making the necessary changes to the software.
As for current vehicles, there's still some collaboration. Despite the fact that Hyundai claimed their transmissions were all new for the 2006 Sonata, they were really (at least in my opinion) nothing more than revisions of transmissions already in use. I questioned my instructor about this point and received an answer something like the friction material being on one side of each metal, instead of having a two-sided friction disc between each two metals. Big deal. In my opinion, although somewhat more refined, there aren't any wholesale changes in the transmissions when compared to your 2000 Sonata.
The 2.4L 4 cylinder now in use was designed by GEMA (Global Engine Manufacturing Alliance), a joint venture between Daimler-Chrysler, Hyundai, and Mitsubishi. I've heard no indications that the 3.3 and 3.8 v6 have design anywhere except Hyundai, but that doesn't imply they're not someone else's engine designs. When Hyundai first began using DOHC engines in 1992, the claim was that they were "Hyundai" engines, when in fact they were nothing more than Mitsubishi designs manufactured by Hyundai, complete with the Mitsubishi design flaws/weaknesses.
I'd have to reread my course materials, but I believe Hyundai is moving toward using Delphi as their electronics designer/manufacturer on all their car lines. I've already seen on 2006 Sonatas-- this would also apply to the Azera and Entourage-- components that now look like they came off a GM product. This doesn't mean that Hyundai is using GM technology, but is likely to mean that the system has again been reverse designed. I.e., Hyundai took a computer system that had already been designed, installed the necessary components (which look like GM components since both use the same system), and made minor changes to the software.