At that time I talked about contour line as a descriptive device that many think of as an "outline". It may be that, but more, its a line describing an edge that often runs across the figure, describing form as well as shape, enriching our understanding of the whole figure.
The background "grills" perform a couple of functions. First, they set the figures in a separate environment of sorts, a defined space that helps us to see shape and form as distinct aspects of the drawings. The grill also calls attention to "negative space". The shape of the area defined by the figure's edges and the edges of the background space or edges of the paper.
If I were interested only in this mind/eye game I would likely dispense with the figure entirely and just work in abstract terms. Luckily (or not) I enjoy representational art, observational drawing and here, the human figure.
Having said all that, we now have to confront an essential truth. In these works we have shapes and lines, color and texture all integrated and/or juxtaposed on a flat surface, but there is no form, at least none in the sense of actual 3D depth. Our perception of depth here, is an illusion we buy into in order to enjoy the story, idea or figure presented. At the movies we allow ourselves to "believe" that the images are real so that we can be led through the illusion of an experience. We enjoy it!
The artist Rene Magritte said it well in his 1929 "The Treachery of Images" a painting of a pipe with the label, "Ceci n'est pas une pipe" - "This is not a pipe". He's saying it's an image, a painting, an idea. (Even the word p-i-p-e is an abstraction) Check it out here - https://en.wikipedia.org/wiki/File:MagrittePipe.j
This brings me to a current problem some artists are encountering. There are anonymous "critics" who pressure the "powers that be" to remove depictions of nudes from the pages of Facebook. Some images have been deleted. The artist/posters are given no chance to defend their work or to confront complainers. The prudes, puritans and religious fanatics, who do not show their faces, do not seem to see the difference between art and reality and do not understand at all the role of the artist. They do not subscribe to the idea, "freedom of expression", the basis of creativity. Check the link below and add your name to those protesting these abusive actions!
Puritanism: The haunting fear that someone, somewhere might be happy." H. L. Mencken
"Illusion is the first of all pleasures." Voltaire
"The space between the dish and the pitcher, that I paint also." George Braque