It's an odd design because it's the equivalent of having a seatpost permanently fitted that has a lot of lay back.
I wonder how that affects the pedalling geometry to have the hip joints further back than usual? Possibly it doesn't make a great deal if difference, although I have used bike fit calculators in the past that suggest there is an optimum saddle position.
I presume the primary intent is to shorten the wheelbase, either for better handling, or to make transportation and storage easier.