This is a limitation of Duolingo. It is a bit erratic, but generally if there is only one letter wrong, ignoring accents, it is marked as a typo, but occasionally it is accepted outright. Your sentence meets these criteria.
If you think this looks suspiciously similar, it is. Usually it is obvious which it means (like one has a verb in) but if you are really devious it is possible to construct a sentence where it is not clear what all the adjectives are doing.