As described in the notes, images taken at a standard focal length (50mm full frame and around 34mm for my crop sensor Nikon) do not tend to distort images. This means that as scenes are approximately as the eye sees them they kind of have to stand on their own without an added graphic emphasis. If not careful then the images can look a bit flat. They have to rely on the composition or have interesting enough detail or activity for the image to work.
Some images taken at approx 34mm (crop sensor.)
Boy with flag.
I find these types of images the hardest to evaluate. Sometimes I am fascinated by a detail or a composition - and then sometimes I find them bland. Also as I change and progress through the course and become more interested in the work of contemporary photographers I find the evaluation all the more interesting and complicated.