I'm not convinced the curly rear stays were of any special technical merit. Same goes for the Flying Gate design; the short wheelbase could have also been achieved by putting a curve into the lower half of the seat tube. More likely these things were done to give the frame a distinctive appearance, as at one time machines used in competition were not supposed to be liveried.
In the absence of the main frame tubes being signwritten, a distinctive frame silhouette would enable a bike to be clearly identified even at some distance.