Exogenous means from the outside. The body produces glucose in sufficient amounts through gluconeogenesis. The nutritional requirement for carbohydrates is 0 grams.

These plants were fibrous, nutrient poor roots humans would eat to not die from starvation when the hunt was unsuccessful. They were probably cooked for hours on end by the women just to extract some nutrition and neutralize the poisons. Ancient humans ate fruit for like a couple weeks in the entire year, the ice age was a thing.

Insulin is not the only anabolic hormone, and protein synthesis is not one of its main functions. Muscle protein synthesis is mostly dependent upon a training stimulus, sufficient recovery and protein intake. Carbohydrates are simply not required to build muscle.

Paul Saladino is a controversial figure. He advocated for a nose to tail diet, which is unnecessary and can be harmful. He concluded, falsely, he needed carbs, while he just needed more protein. And then there's also the whole liver king drama I don't want to get into here.