Lumping anything written in meter and verse into the group "poetry" that cannot be translated is a bit ... something. Mallarmé, maybe. Chaucer? I find it hard to believe. I have read some of it in the original, and I did not find that much difference. It may be that this is a very good translation, and I am fairly sure it helps that it is translated into a later version of the same language.

I know my enjoyment of it would have been impaired if I were to read it all in Middle English: it is too close to Norwegian. When I read in English, I think in English; and when I read in Norwegian, I think in Norwegian. And when I read something that looks like English with random Norwegian in an odd spelling, my brain goes kaplooi.