A French national suggests that DURANT emphasizes the such and such occurs/occurred from the very beginning of the time interval to the very end, while PENDANT does not. This seems to be the difference between "I spent the entire week doing such and such" versus "I did such and such during the week."
If that it is the case, there may be value in adding that to the lesson. I have noticed BTW that DURANT appears in conversations much less that PENDANT, perhaps because of the nuance cited above.