That good night: gift or punishment?

[Raynor]

apparently Tolkien had the Myths Transformed chronology in mind when he wrote the Athrabeth.

I don't think so; Tolkien dates the debate around year 409 - which is in accordance with the chronology of the Years of the Sun (i.e. between the emergence of Glaurung (260) and the Dagor Bragollach (455)). According to the Silmarillion, in year 1 Fingolfin's host reaches Middle-Earth "at the first rising of the moon"; if the moon didn't indeed first rise then but much sooner (and if the Men didn't awake in that year), why would anyone reffer to that year as year 1?

Moreover, it is stated by Christopher in Atrabeth's notes that: "It was of course fundamental to the whole conception of the Elder Days that Men awoke in the East at the first Sunrise, and that they had existed for no more than a few hundred years when Finrod Felagund came upon Beor and his people in the foothills of the Blue Mountains" - which is in accordance with his comments on the Myth's Transformed revised astronomy.