That isn't how genetics work. There's no need for purity of blood to awaken a powerful KKG, Boruto and Himawari are clear examples. Naruto isn't a hyuga.
I am sure its covered however its so insignificant to the original story that I don't remember where exactly.
Exactly.
Purity of blood is a necessity. In the Itachi Shinden novels, Izumi struggles with her Sharingan due to her diluted heritage. The weaker the blood gets, the less the body is physically accustomed to the use of the bloodline. The Kekkei Genkai doesn't immediately attune itself to the physical capabilities of the user. You either have the proper genes to handle and use it or you don't.
Not only does diluted blood reduce the chance of awakening your gift, but it lowers your capabilities of fully using it.
Boruto and Himawari are half Hyuga, that is enough blood for one of them to manifest the dojutsu. A Hyuga with only quarter or even less blood will probably never awaken the eye, much less even be able to use it properly.
You don't understand genetics, just stand down.