"The fruit did not rot"
Both should be accepted. If I have two apples and a banana and you say you're hungry, I'm more likely to point you to "the fruit over there" than anything else. As such, both matunda and tunda can be fruit (countable singular and uncountable), but only matunda can be fruits (countable plural).
Hmm, my first assumption was plural pieces of fruit, but you're right - both should be accepted.
Yeah, as far as I know, none of the error reports have been implemented yet. The creators are busy with the Peace Corps. Don't lose hope!
(Also, you don't have to be sure you're right to report something ... nearly sure is enough. I'm sure the reports for things that are actually fine are annoying, but better than leaving things unreported. I mean, don't go overboard with it and waste their time, but the point is that we're drawing their attention to it ... when they eventually get to it.)