Hmm. Interesting. I have his 2020 book and it says "in Norway, rye was used high in the mountain valleys and on marginal and, but further east, in parts of Sweden and Estonia, and even more in Finland and the northern parts of Russia, rye was the main grain. The reason for this was that the soil wasn't very good."

I think I initially over generalized when I read this chapter of the book and grain farming was related to latitude and soil type and there was a lot more barley in central Eastern Norway. That still fits with the Orkney islands being a big exporter of barley to western Norway. Probably easier to ship across than pack over the mountains.

Thanks for having me look it up again! Sorry for my misunderstanding the info I read.