Lets think about something here because I am going to blow your minds:
Now these scans show us one thing:
1) Everyone is born with a specific type of Nature type, which the paper picks up on and reflects.
But... KKG's require 2 Chakra types? And this is where we can draw 2 conclusions:
1) A person is born with a KKG and 1 Nature type and must learn another one of the required styles to make use of the KKG.
2) A person born with a KKG is born with 2 Nature Types and thus has an easier time using mixed Nature styles.
I believe the Latter because Haku was roughly the same age as Sasuke if not younger. Yet Sasuke was not only born an Uchiha, giving him an advantage but also is fueled by the hatred of his brother killing his family thus driving him to improve quickly. So if point 1 is true then we must believe that Haku being younger than Sasuke was able to learn Water and Wind then Master Ice before Sasuke could even master Fire Style? Is that logical?
Or perhaps he was able to learn Water and Wind quickly because he was born with them as Natural Styles making it easier for him to progress to Ice. Now to me that makes sense, but it also validates my theory in a sense.
Because that means that using Mixed KKG isnt limited only to people born in specific families but it is open to anyone who can master them but is easier for people born into certain families as they start off with 2 Nature Types as oppose to just 1.
And with this I debunk the main challenge to my deductions train of logic.