The real issue here that original attention span is about moral or other judgement. It is about making claim of disapproval over media use rather then anything you could measure.

> Contrast that with a university lecture, where if you zone out for 15 minutes you might never catch back up because you need to interact with the material in your head to be able to consume it properly.

Zoning out university lecture was extremely normal when I was studying over 20 years ago. You did not died either. You kept making notes in a zombie like state and then reread the notes later on. Or you checked textbook or you asked friend for notes. It would be pretty rare for your memory to be the only source of learning later on.

There was no need to understand and acquire the lecture content right at place during lecture. In all likelihood, there was never ever such need.