The current guidance for using this tag is "highway which has lanes=* with any value below 2, e.g. 1 or 1.5". There are many two lane roads that do not allow passing by using the opposite traffic flow lane (marked by a double yellow center line in the United States). In order to legally pass, one must wait for the person ahead of him or her to pull out into a turn-out.
I feel that these should be marked on these two lane roads much the same as on a 1 or 1.5 lane road since passing points will be restricted.