I think this is the crux of all the other socio-economic superstructure arguments the article's author makes. The assertion is that Tolkien's fantasy world of wizards, wraiths, walking trees, dragons, invisibility rings, dwarves, elves, etc would have a realistic medieval material production culture.
In order to imagine an idealized/fantasy bucolic shire, wouldn't Tolkien just imagine soil that's more fertile and nutritional crops with higher yield? Would this be the furthest he asks the reader to stretch their imagination?