XData, YData, CData, Fun Data! - single pixel image width

What would you expect the image limits to be from this function? (before running it):

imagesc([0 1],[1 20],rand(1,10))

Am I missing something in the documentation on this?

I ran into this method of XData,YData being used by the colorbar (In that case with xData where as here the interesting result comes from YData).