Not sure if this is an indication of how the base-card reveal was normally handled in a sudden-death situation, but the final episode of Perry's Card Sharks reverted to one-question sudden death to finish the match on time. In the second round, no cards had been revealed, so Jim flipped the base card of the player who won the question and then gave the option of play/pass with the other base card hidden.
But, then, on the Rafferty version finale, Bill had two rounds that were one-question sudden death. Both base cards were revealed in what might be the only pre-2019 card turn by a dealer.
The Eubanks version ended with Peckerhead's girlfriend playing the Money Cards after a standard match.
As for video of the base card going unrevealed until sudden death in regular gameplay, it is still elusive. I suppose it is possible that each of these reveals could have been correct for the unmodified rules for each series.