Can anyone explain the content advisory?

They have little bits of string tied around their waists which hang in front of the genitals, which don't do much to obscure the camera's view.

That statement must have been made by somebody who correctly understands that nudity is a cultural concept, not something about the amount of fabric somebody wears.

For example, an American and a Korean woman might mutually perceive each other as raunchy, while being sure they themselves are dressed appropriately (legs v.s. cleavage; illustration: http://japanfocus.org/data/1.1_8.PNG).