The Japanese Wikipedia is not a translation of the English Wikpedia. Wikipedia isn’t a good place to learn a language, and especially not by comparison. For example, here’s the Polish Wikipedia page:

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Oh, and here’s the German Wikipedia page:

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…hold on, that’s not right. Both Wikipedias have a disambiguation page, and the first link on them goes to their equivalent of Simian. The point is, every Wikipedia has its own structure, its own rules of what should be a page, and articles might be based on sources in that language, not in English.