I'd agree it's low on overall grams of protein (for a male, at least) but he did manage to get the amino acids that non-meat diets usually lack... so it's not a total fail.
Most vegetarian diets do not lack sufficient amino acids. Protein needs are greatly exaggerated by "pop science". Iron and B12 are of greater concern than protein in non-meat diets.
Most contemporary diets are low in iron because people don't eat their dark leafy greens, which are, far and away, the best source of bioavailable iron. The OP diet, which is heavy on broccoli, neatly avoids this.