That's not true, at all.
Not all KKG are elemental, Sharingan and Byakugan for example..
But all KKG are certainly bloodline limiting and can only be used by a certain bloodline..
KKT is a bloodline selection meaning it's not limited to a certain bloodline but to certain people in different bloodline..
That's why Muu and Ohnoki can both use Dust Release although they are not related
So it's not just about having the elements, it's about the ability to combine the elements
You need certain genes to have KKG, but KKT could be taught. Although, we've only seen one KKT in the whole series so it might be limited compared to KKG.