Martin wasn't a very good fighter (he had worse than a 50/50 win-lose ratio), but he was known for being very hard to kayo. He went the distance with Foreman, Klitschko, Witherspoon, Tubbs, Hide, Holmes, and Moorer. Thus, whenever American fans heard that someone stopped Martin by a genuine kayo or one sided TKO (not including stoppage by cuts or injury), we tended to think that the guy who stopped him must be a pretty serious puncher. That DuPlooy beat Martin inside-the-distance is obviously more evidence that the South African could bang.
That fight was an all out war. I remember DuPlooy just being totally, utterly exhausted and basically just saying "No more", like an Andrew Golota kind of move. DuPlooy was like a Tommy Morrison. They tried everything to make him a star, gave him every chance, maneuvered him as best they could, but he still couldn't break into the big leagues.