Technically, yes you can draw an object with only one entry.

In an SVG renderer, the "pen" has a position that starts at a default location.  You can then tell the svg to, say, "move to point x" or "draw a line to point x" or "draw a curve to point x with control points y and z".  So, for example, a path with one point might just tell the renderer to draw a line from wherever it happened to be previously to the specified point.  Probably not useful, and it would never come up in matplotlib paths (as far as I know, all matplotlib paths start with a "moveto" command), but it's technically possible.