I too am struggling to understand this use of undo.

If I'm reading this correctly it means applying a large number of undos to get to a previous editor state, followed by an equally large number of redos to then get back to where you started.

I can't recall every doing something like this.

The only time I seem to use undo is when I genuinely make some sort of editing mistake.

One reason I know I don't subconsciously do this is because I never struggle to execute an undo action.

However, on the rare occasions I need to do a redo I tend to struggle with the short cut key and usually go to the menu instead.

That tells me I use undo much more than redo.