I’ve found that instead of dropping reference images straight into the default Blender view port, change the view port first to the working orthographic view port. In this case side view facing left (click X on the gizmo). Now when the image is dropped into Blender it aligns with this camera in this view port (Grant alluded to the camera alignment). This saves any rotation. It just needs scaling and positioning.
Yes, this can make it a bit easier and faster. Remember you can also use numpad 1 to jump to front view and numpad3 to go to side, this is even faster than clicking on gizmo
(Ctrl-1 jumps to back view and ctrl-3 goes to other side)
Yes I always work that way.
While Grant shows it is easy to correct if just randomly dumped in, it seems easier to just do it straight in the first place.
That is true you can first select the correct viewport before you drop in the image; but I think Grant was trying to introduce the student to the clear rotation/scale/rotation tool, because he must have guessed you would eventually figure this technique out on your own. And if you do forget (like I do when I have been away from sculpting for a while) it is good to know how to easily fix it (other than doing undo and starting over in the correct viewport.)