The rating system is awful and arbitrary, who cares what words they don’t like? Actually, the rating system legitimately is sexist. Exposed breasts of a woman will get you an R these days while the exposed chest of a man wouldn’t even push it to PG.
Have you visited a public pool or a non-nude beach? Have you noticed at those places men are topless but women are not? Men’s and Women’s bodies are different. A man topless is not nude. A woman topless is nude.