Humans are omnivores because it is an observed current and historical fact.
Human tribes have survived largely carnivorous or largely plant based lives.
Body builders range from largely carnivorous to largely plant based.
Humans as individuals are flexible and have grown, survived and reproduced on varying conditions.
It is due to human flexibility that we rule the world.
----
Back to this raw vegan family. Right now they feel good in this diet so they are sticking with it. They are currently in that mindset. Just like some people here who used to do the vegan thing, they are in that mindset and have to be jarred to wake up that extreme diets are a temporary thing. As Stanley Bass said, all extreme diets have value, they have limited value.
In their book they eat hemp seeds for protein. And they supplement with Vitamin D and K2 depending on the season. They know of raw families who supplement with raw eggs, raw goat and raw meat.