You have to be a judo nerd to get it.
One way to win in judo is to score ippon, which is like a pin in wrestling or a knockout in boxing. The definition of ippon is to throw the opponent so that he lands largely on his back, with force and control.
Douillet attacks with uchimata, which is a throw somewhat similar to a whizzer in wrestling. The idea of the throw is to sweep away the leg and spin him onto his back - like this.
There is a counter to the throw called uchimata sukashi, where you make the guy miss with his sweeping leg and spin him over and land him on his back. This is considered very elegant judo in Japan, since it uses his momentum against him. It is much less common in the rest of the world, especially in Europe, where power judo is more common.
The controversy is if Shinohara countered Douillet with uchimata sukasha, or if Douillet made a partially successful attack. In the linked video, it was called ippon for Shinohara, then changed to yuko for Douillet (a lower score than ippon - the scoring system in judo is kind of bizarre). The Japanese were adamant that Shinohara had scored, but lost the appeal. Douillet won the gold.