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You have to read other comments. Germans would also generally say Du trinkst Milch, this is, however, a specific milk. I'll repeat an example I previously made: Are you drinking the milk I gave you? It's a bit confusing without context but it definitely means: You drink the milk.
Sorry no, the Duolingo team is very unlikely to make a mistake having to do with gender (I started Duolingo years ago and have seen practically every sentence on here, I have never encountered an incorrect gender being used) or something simple like that.
Nevertheless, you could definitely say Duolingo makes mistakes, most commonly with sentences that, while still being grammatically correct, sound unnatural. Also, the Duolingo voice makes blatant mistakes all the time, but this is one they can't control.