I don't think this is true. By "Middle Ages", I'm guessing you're referring to the period from 1185 to 1600 (https://en.wikipedia.org/wiki/History_of_Japan#Medieval_Japa...). I've been working on translating two classical Japanese texts on my blog (http://www.kakekotoba.com/), one from the 1830s (http://www.kakekotoba.com/2012/08/introduction-to-shunshoku-...) and one from the 1100s (http://www.kakekotoba.com/2012/11/introduction-to-konjaku-mo...).
If you look at the texts, there's a huge difference in the writing style, which is partially due to the nature of the content and the target audience. As more people became literate, there was a marked shift in how Japanese was written.
I don't think this is true. By "Middle Ages", I'm guessing you're referring to the period from 1185 to 1600 (https://en.wikipedia.org/wiki/History_of_Japan#Medieval_Japa...). I've been working on translating two classical Japanese texts on my blog (http://www.kakekotoba.com/), one from the 1830s (http://www.kakekotoba.com/2012/08/introduction-to-shunshoku-...) and one from the 1100s (http://www.kakekotoba.com/2012/11/introduction-to-konjaku-mo...).
If you look at the texts, there's a huge difference in the writing style, which is partially due to the nature of the content and the target audience. As more people became literate, there was a marked shift in how Japanese was written.