There is a really funny glitch in the slow version of the audio for this sentence. The TTS actually reads out the hyphen at the beginning of the sentence, so it says:
"Punct și virgulă poftă bună Ana mersi."
It is also confusing because a "punct și virgulă" is a semicolon, not a hyphen, so perhaps it is a double glitch.
You're right, it should be accepted, especially because "bon appetit" is borrowed from French. If you wanted a direct translation, you would have to put in "Good appetite!" But we don't say that in English. Although "Have a good meal!" conveys the same idea, I guess they're looking for a translation of the phrase, as opposed to the meaning. I don't agree with it, but it's up to the creators of the course to make the lessons the way they want to, I suppose.