Common Pink Sheep

A few years ago I encountered something in single player that was very peculiar to me and I have never encountered anything similar to it again and I do not know if it was a bug or not. I was exploring seeds (randomly generating them) in creative mode and eventually came across a seed that caught my eye. For whatever reason this seed contained pink sheep, upon pink sheep, upon pink sheep. I believe that there was at least 1 pink sheep per group spawn of sheep. Pink sheep are extremely rare, so I believe that there is a piece of code somewhere that caused this. Can anyone please explain if this is a bug or not and what caused this to happen? This has been popping into my mind when playing Minecraft ever since the event took place. I would test to see if this was still a thing in Minecraft Java 1.13.2 and as far as I know it should be, but apparently this is an extremely rare occurrence. I will update this issue as I search through seed data code.