Typically the vegetables are also dead when you eat them. "Don't eat dead things" is a moronic statement dreamed up as an attempt at shock value. It doesn't mean anything and can be safely ignored.
But in practice don't most people mean tofu when talking about soy beans for protein? That tends to come out at 10-13g per 100g. Same for cooked cans of soy/edamme beans and most other canned lentils/pulses? I've never seens 30g per 100g for cooked canned beans in reality.
I eat a high protein, vegetarian diet optimised for lifting weights, and "Approximately no additional grams, if you pick the right legumes." doesn't really add up for me. For the main sources of protein I usually try to eat daily:
and then also supplement with whey protein powder to get to my daily protein target (~150g). To get there with just legumes I'd need to consume 15 cans of cooked lentils (i.e. not achieveable in reality).
I also eat those yes. Something I don't see mentioned for a high protein diet often is gram flour. 22g protein per 100g and can be made into socca very quickly and easily with just water and small amount of oil.
Beef is dense in some nutrients but it certainly is not more nutrient dense in general. Plugging food into cronometer.com should be mandatory in HN nutrition discussions.