Dharmakaya is not this virtue. Dharmakaya is the essence of Buddhahood and formless in nature.
Sambhogakaya is this collective virtue that you speak of and a highly cultivated person can "show it off" so to speak in a physical manner.
That being understood, your question:
Do any traditions claim that the dharmakaya is never manifest in a human being?
With the proper above understanding in place, your question is actually about the sambhogakaya which is like a collective strength of one's paramitas.
No one has absolutely 0%, maybe some very very low. If one is lucky enough to be a human being, then they definitely do not have 0% and have done some great good (maybe lifetimes ago) to deserve being human.