maybe you just had luck finding a shiny? you dont have to chain shiny you know. I have tried that fishing method the whole day in different ways without any luck. and I have 7 boxes filled with non shiny Eevees.. And a box with two shiny pokemon that I just stumbled over while not looking for shiny.. Im not saying that your method doesnt increse the odds.. Im just asking how you cant be absolutely sure Heck I dont think that anyone actually can verify that everything works exactly the same as in earlier generations yes.