What on EARTH do you eat to hit those macros? If I eat the minimum healthy calories (1,500) entirely in broccoli, I’d be >50g of protein (~0.6 g/kg at 160lbs). What kind of meal plan gets you low net carbs AND low protein? Are you drinking olive oil or something?
But yes. To answer your question, you do eat a lot of food that is 100% fat or darn close. You will see menus like "2 eggs and 2 tablespoons of butter". The vegetarian version will involve a lot of avocados and coconut oil. You don't have to eat it straight, and most meals involve combining a massive amount of fat with a small amount of protein or fiber or something.
You're right though, I think vegetables have more protein than people are led to believe, especially since the health/fitness industry make it seem like you need to be ever vigilant in getting your protein numbers up. Meanwhile, the average American accidentally eats far more than they need and certainly doesn't need to resort to supplementation.
Broccoli has only 3 grams of protein per 100g (and 7 of carbs), I don't think it is particularly high, and 1500 calories of broccoli would mean eating more than 4 kg of it.