OTOH, you won’t see many bodybuilders at the highest competitive levels that are vegan. (Compare the physiques of the people you see when you search for vegan bodybuilder with Mr. Olympia 2023 images.; while yes, absolutely, everyone in Mr. Olympia is taking metric fuck tons of drugs to get huge, there shouldn’t be anything preventing a vegan or vegetarian from doing the same.) When you are being absolutely scrupulous about hitting your macros, getting sufficient protein on a bulk cycle without also getting high carbs or fats is very, very difficult on a vegan and vegetarian diet. The stereotype of a BBer eating nothing but boneless, skinless chicken breast, brown rice, and plain steamed broccoli during a clean bulk or cut is pretty accurate, because that makes figuring out exactly how much protein, carbohydrates, and fats you’re eating really simple. If you’re trying to do a very clean bulk or any cut, you’re going to need to avoid food that has multiple ingredients unless you’re planning on weighing everything that goes into it first. Which also fucks up your recipe, but, oh well.
If you’re a power lifter, it’s less of a concern; you may be getting more carbs or fats than is ideal, but since you aren’t trying to cut to 5% bodyfat, that’s not really a huge problem. Same with endurance athletes (who, TBH, need to eat significantly more fats and carbs anyways; if you need to eat 8000 cal/day just to maintain, then eating super clean is probably not a concern).
Take your example of hemp seeds: for 30g of hemp seeds, you get 10g of proteins, but you also get 15g of fat. For 100g of dry lentils, you get 27g of proteins, but also get 60g of carbohydrates (48g net carbs if you subtract fiber from your totals). For 6 oz of B/S chicken breast, 53g of protein, and 3g of fat. (…Which is slightly better than ON whey isolate powder, which has 1g fat, 2g carbs, and 24g protein per serving.) So if I’m trying to hit 250g of protein in a day, it’s easy to say that I need about 28oz of b/s chicken breast each day, and do my meal prep all in one go for the week. It gets more complicated if I want to have lentils, quinoa, brown rice, and asparagus.