There's no specific criteria, and that's the problem of the article. Pubic hair used to be regarded as "obscene" in the old days, so, paradoxically, uncensored child porns without pubic hair were legal in the 80s. That standard changed later, and even researchers of the censorship don't understand what the authorities are thinking of.

In most films, their problem is Eirin/ Film Classification and Rating Organization's censorship rather than the article 175. Anno put spinning Eirin mark at the introduction of the film. It's like he's saying, "Yeah, we passed their censorship. They don't know what they're watching, lol." EoE even got G-rating, so elementary school kids watched EoE at theaters. Some fans wrote their worries on magazines in those days. I don't get why they rated EoE as G.