So, scientists don't really know what the optimum amino acid balance is for human beings. They decided years ago to call eggs the perfect protein, since they provide the perfect balance for a chick embryo, and everything else is measured against eggs. So rather than being a measure of how good a protein source is for our body is, this is a measure of how egg-like the amino acid balance is.

Except in cases where malabsorption is an issue, almost any whole food vegan diet that provides you with enough calories will provide you with enough protein to avoid malnutrition. (Whether you believe it is the optimal levels for your body and lifestyle is different. Of course you must test what works best for your unique biome.) The exception to this is a diet that is solely fruit-based and possibly a diet that is solely cassava-based.