Around 2:10, it’s said you’ll need to modify each pillar separately but there’s an easier way! Since the pillar is the same on both ends thanks to the mirror modifier, blender has a mirror editing tool as well! it’s in the upper right corner. It looks like a butterfly, since the object is mirrored on the z axis, click on the letter z and then edit, and you’ll see both ends change as you move the pillars edge!
