D. kaki x D. lotus = “successful, but not rewarding”. To me that just means that the F2 and F3 generations are where the rewards would happen. That is often the case. In the first generation you just get a 50:50 cross, but in the second and successive generations you can get enough mixing that some plants will possess certain traits from one species or the other like perhaps the full hardiness of D. lotus and the full large fruit size of D. kaki.