In order for the type to overlap, the center to center spacings between type blocks must be less than 1/2 the width of the two blocks. First this requires proportional spacing, and second, unless your typewriter has memory the designer cannot allow this, because you must have kerning or you cannot guarantee that you will not get overlap of typed characters (i.e. you must have knowledge of kerned pairs).
Perhaps your Courier font is different from mine, but on my computer the two "M"'s in the Courier New sample definitely touch each other, and there is definite (albeit slight) overhang on the characters in the second column.
To confirm this latter point, select characters individually and note that each extends just past the edge of its selection box. Given that the selection boxes are directly adjoining, this implies that they overlap (albeit by only a pixel or two).
You are correct in your statement that kerning is necessary to allow characters to reach beyond their escapement boxes without any possibility of overlap, but because characters CAN overlap this is generally not a major issue. Unlike lead type which can be damaged if character glyphs overlap, computer type has no such limitations.