GM's design director from 1986 to late 1992 was Chuck Jordan. It was during Jordan's time that the designs for the cars featured in this post were established. The more important design was that of the 1995 Oldsmobile Aurora, the 1995 Buick Riviera being based on the same platform and sharing its basic characteristics. It might be said that there was only one basic design, wherein the Aurora was the four-door version and the Riviera was the coupé version.
In the essential book A Century of Automoble Style, Michael Lamm and Dave Holls (who worked for Jordan) state the following regarding the Aurora (page 282):
Another car Jordan pushed through was the 1995 Oldsmobile Aurora. The Aurora began as a non-divisional project in one of GM's advanced studios. "We said, 'Let's design a sedan the way they do it at the Lockheed skunkworks--an aircraft theme,'" he noted. "We called it the 'tube car.'" When the advanced designers had finished, Chuck had a full-sized fiberglass Aurora mockup parked at the head of the Design Staff escalator. "That's a place of influence," remarked Jordan. "You pass by there so many times a day that the design either wears well or it doesn't." The design wore well, and when Oldsmobile decided it wanted a four-door Toronado, the Aurora came up as a natural. It too went through a rigorous clinicking process [where potential buyers evaluate a number of real cars and styling mockups with brand identification removed from all the vehicles].
The Aurora received generally favorable reviews, but was only modestly successful in terms of sales. Rivera sales also were mediocre.
When I first encountered an Aurora, something I immediately disliked was the near-symmetry of the front and rear doors. This feature seemed static and dull, and helped emphasize the nondescript appearance of the car. The front end lacked character and brand identity. The red tail light and reflector assembly shape seen in the lower photo only served to emphasize the soft, droopy, characterless rear body shaping. Although the project was well-intended, good intentions do not guarantee success; the Aurora's relative market failure did not surprise me.