Per the CDC site, Protein, the recommended range is 10-35% of calories from protein. They also cite 56 g for adult males, which, on a 2000 calorie diet, would be about 11.2% of calories. Thus, it’s close to the minimum healthy intake. I think they do this partly because people in generally like to consume a lot of high-protein fatty foods, and they generally need to be reminded that we don’t really NEED all that much.
That being said, the range is wide, and extra protein has some benefits, ESPECIALLY if your body is changing. If you’re trying to put on muscle and exercising for it, extra protein helps, a great deal. Conversely, if you’re trying to lose fat (and so eating reduced calories), but trying not to lose lean tissue, again, extra protein helps a great deal. So your goals matter.
Also, a meal with very low protein tends to be less satisfying for most people, so keeping the protein level up can help people avoid feeling hungry on Soylent. Soylent’s 114g of protein, in a 2000 calorie diet, is 22.8% of calories. That’s solidly in the middle of the recommended range.
Note: if you’re consuming more protein than you need, but getting the correct number of calories, then you do not pass excess protein in your urine. Rather, the body converts the protein and you burn it as energy. If you overeat, consuming excess calories as well as excess protein, then you’ll be passing excess protein through your urine, which can be hard on the kidneys.