Oh, you're one of the people that believe that a perceived "sugar rush" has something to do with diabetic glycemic excursions? They're entirely different phenomena. Dismissed. But thanks for the irrelevant link!
I'm going to answer your first question with a question: what do you think he means by "nasty crash"? Because I guarantee it's not what happens post-excursion.
There's no difference -- postprandial excursions are a diabetic phenomenon, and have nothing to do with what non-diabetic individuals think of as the effect of sugar and fiber on their health and mood.
What is the difference between a diabetic glycemic excursion (what you said) and a postprandial glycemic excursion (what I linked)?