This concise formulation of the rule indeed fails to cover edge cases like yours. The rule is actually meant to exclude single posts made by people in other languages - it allows moderators to delete them without having to understand what is in them - and to have people from other countries "hijack" the conversation and carry it on in a different language.
So, I would propose to understand the rule as "Your post should be easily understood by an English speaker" (with other languages allowed for the language specific sites on the network). This means that you can make posts concerning untranslatable concepts from a different language (e.g. Is it possible to make kataifi dough (by yourself or starting from filo dough)?), or explain translations as in the question you linked. As long as the post is usable by an English speaker, that's not a problem.