I should add that there have been proposals to explain the choruses, they just have not convinced people.

The Collinson text is fragmentary; if we didn't have the other texts, we might not have recognized it as related to the "Orfeo" legend. And, like all four surviving versions, it does have some odd-but-understandable words in the verses. My book has a glossary for that part. Also a reconstruction of what the original text looked like, as best it can still be reconstructed.