If they did, then they weren't in a persistent (or permanent) vegetative state. Perhaps the person was in a minimally conscious state or a coma.
Minimally conscious was only a term being added to the medical lexicon around the time of the later court cases with Terri.
Your point that the people were misdiagnosed is a real thing. It happens all the time. Years before the MC designation, PVS was the only one that was used after about a month in a VS. Studies from the old days showed that the diagnosis was wrong at least 40% of the time. That’s too much. I think that’s when the experts started looking at other ways of measuring brain activity. There’s still so much to learn.