[bitshiftfaced]

That sounds plausible. You also see an abundance of center embedding in older philosophical works. In highschool I tried reading through these, and they way they write forces you to read slowly and constantly backtrack.

I think you see it with more complex subject matter because you have more tangents shooting off. It means the writer needs to think ahead and do more mental work in order for the sentences to be read more easily. It was also more burdensome to edit your manuscript back then, so you had physical as well as mental friction.