I seem to remember way back in the 1970s in the World Cup the West Germans and Austrians both needed a draw to go through to the next round so just kicked the ball back and forward for 90 mins. There was a huge outcry. So nowadays to minimise the chance of that happening the final games on qualifying groups are played at the same time so it is less likely that someone knows what score would take them through. I'd think for the badminton thing you could either play the decider of one group at the same time as the decider of the other group - or better still do away with the seedings altogether and just make the draw for the next round after all the contestants are through.