I guess it's because there are two ways to find displacement. He didn't use the xf-xo formula. He added up the values to get the net displacement instead. Maybe if this question was being based on a number line, the xf-xo formula would be used aswell. Hope this helps :)
2023-03-12 04:10:54 +0000 UTC
At minute 6:14 for the displacement why did u start with the starting than the ending wasn't it supposed to be final position- the initial position?