for one thing, the WHO RDA is meant to be the minimum to keep you alive. That's not optimal, that minimum. If you do exercise or do sports, your needs are a good bit higher. A number of studies have found the .6g per pound range to be the minimum for people doing strength and/or sport training to not lose muscle tissue. You can ignore the specifics of ratios of those so long as your protein comes from a variety of sources as the differences in ratios between different proteins will help cover it.