Most likely the Walrus was fitted a normal engine, that is, in rotation direction. I looked through many pictures and when looking from the tail to the front, the engine was turning clockwise, which I think was the norm at that time for British engines. That meant You needed a "reverse" or pusher prop on the tractor setup of the Walrus.
Most likely they wrongly (reversely) installed a NORMAL prop....
It IS quite confusing though, I had to take out a normal and a reverse (model airplane) prop to check if I wasn't talking nonsense!
I also stumbled across this picture, OK, it's just a plastic model, but that one must have been one hell of a fast backwards flying "aeroplane"!
https://www.pinterest.co.uk/pin/360710251396858307/