It is true, and shocking!
I had lunch with him and Tony Drago during Interpool Open, and I asked him if the rumour about him making 27 racks in 8-ball was true.
The face of Tony Drago was priceless when Ralf Souquet said yes, and explained that it was bad contact that stopped him from getting position on the 8 in the 28th rack...
I have heard that Thorsten Hohmann has an almost similar run in 8-ball, but I am not sure...
During European Championship in Stavanger in 1997, Germany was in the final against Denmark in the Team Competition. Ralf Souquet played 8-ball and ran 10 straigth racks to win 10-0...