I found an image online of the picture which I believe was in 'Race Car Engineering' by Valkenburg.
It's not a great photo but neither was the one in the book.
You can definitely see how the flow is displacing over the very steep aft-body.
Ludwig Prandtl and Oskar Tietgens were able to keep flow attached over a wing flap at 40-degrees of inclination by use of suction.Prandtl had demonstrated the concept with cylinders as early as 1904.
