I agree that it's dumb, but it's probably not entirely Steam's fault. They have the difficult job of making the games they are selling compatible with many dozens of different jurisdictions, each of which has different, sometimes vague rules. Some of these rules are so new that the locals haven't figured out yet how to interpret them. Breaking such a rule can have severe consequences. There is a chance that the local authorities enforcing these rules do not speak English and operate with translations that render "girl" as a word that cannot refer to an adult woman, only to a child. Either by accident or intentionally to solicit a bribe or unfairly prosecute Steam.
For example in Germany, the rules have become so strict that Steam has basically given up. The vast majority of adult-only Steam games cannot be bought at all; their store pages return an error in Germany and you need an external search engine to even find out that elsewhere they are available on Steam. A few are available in a censored version only. Also lots of older games are no longer available in Germany despite having no adult content at all, just because the developer could not be bothered to fill in the affirmation to that effect which recently became a requirement.
If they don't want to give other countries a similar treatment as Germany, Steam must be extremely strict. It's not practicable for them to have different rules for different countries. They need a single set of rules restrictive enough for all countries that don't get the Germany treatment. Any relaxing of the rules would probably mean that there is an additional country where they can't sell adult games at all.
Sounds like a
them problem, though. If they have bad translations (software or otherwise), they need to get it fixed. Something like "girl" in English referring to an adult woman is as common as "man" or "dude" meaning any person ("Come on, man!" or "Dude, what a piece of crap!"). Developers can't be held responsible for Steam doing a piss-poor job of translating content. What's more, there are things like Japanese-language-only games sold in the United States, so I see no reason why games on Steam can't be in English without any translation provided. For anyone playing who
actually knows English (fluent, not just proficient), there would be no confusion whatsoever.
To be frank, I think what you've described is far more than a problem with translations and multiple jurisdictions. This is a problem of control. Individual nations wanting control over content coming from another country. If they have such a big problem with it, they should just block stuff from other countries. And if citizens of those countries have a problem with what their governments do, they should seek for change if possible. For instance, obviously not all places have this option, but if they can vote out stupid anal-retentive prudes, they should.
I see no reason why anyone should have to censor their content because of some cultural difference. Different cultures view things in different ways. If you — whether as a personal decision or as a cultural influence — have a problem with how something is done elsewhere, just don't get that content. Trying to have government force companies to self-censor, effectively taking over the job of that nation's individuals practicing a modicum of self-discipline, is one of the stupidest things humans have ever come up with.
Again, because
Nudist College is written
in English — and because in nations with English as a first language
there's absolutely nothing wrong with the terms school or girls, or in showing students in uniforms while in school — no changes whatsoever should ever have been required of Elsa. Steam is dictating an author's creativity at the behest of stupid governments who are too intolerant to understand that other cultures exist and their own way isn't "the only right way".