Odds are what you saw is an engineering test article, not flight hardware. Test articles would typically include the same computer systems and some common things like the drive train, but wouldn't be built to the same standards as flight hardware. These test articles are very useful for testing command sequences, computer fixes, etc. Most of the time, they're too heavy to be launched, like the Enterprise shuttle that was used for the captive carry and glide test flights back in the 1970s.

Now, those systems on the test articles that are identical to flight hardware could be moved to flight status for a future flight. However, by then, it's likely that better systems will be available based on the lessons learned from the current rovers.