I have failed beginner Duolingo exercises in a language in which I'm fluent, due to it quibbling over something that truly could be translated in several different ways.
It's the same on CodeCademy with some of their exercises. "Well shouldn't it really be like this?!" No. The accepted answer works fine. Don't over-engineer a simple solution.
While I could see where it was coming from, this would be incredibly confusing for a beginner, who wouldn't even know to report this as a problem - they might conclude that "piece of bread" was just incorrect.