For Italian the main issue in reading is open vs closed vowels, but those are also different between accents and it's expected that two speakers will use them d

For Italian the main issue in reading is open vs closed vowels, but those are also different between accents and it's expected that two speakers will use them differently without hurting intelligibility. So in some sense the ambiguity is a feature and not a bug, and the paper acknowledges that it's more of an issue with the scoring formula.