i think you were just really really really lucky.
The best Pull i had so far was Japanese Iris, Queen of the Night and Flowering Peach at once but after that i have got only Dupes ( 1x Lupine, 1x Waterlily, 1x Bipinna Cosmos, 1x Japanese Iris and 2x Queen of the Night)
Bipinna Cosmos failed to get her Skill Level Up but she is my least favorite Knight anyway ( Sry Bipinna Fans but i think she is one of the weakest 5*)
On Saturday last week i have finally got Chocolate Cosmos (not a Dupe) and in my opinion much more usefull than her cousin.
I am assuming that the RNG in this game is time based or something.
If they decrease the Gacha Rates even more i would quit this game.