ITS THEORY TIME

I want to write my own fan fiction and so I searched for good Evolution lines and Partners for my seven Kids. But then I noticed something strange. According to different sources a few Digimon are on two different levels?
Just like Whamon. Whamon is a Champion Digimon, but also a Perfect?
But thatís not all. Piemon, Minotaurmon also has this faith.

Whatís your theory? Is there anything explained?
Is it possible that levels donít have clear lines, like we used to know?
Does any Ultimate/perfect Level digimon habe the possibility to be also a Perfect/champion?