That is true. Not a huge difference, but yes, when you expand you get a predefined set of land. Not to say that would be a better design than what 0ad has (i do like how it is now), but i imagine predefined sections would be good for ensuring one cannot create too many chokeholds, as well as preventing those annoying situations where you expand, but can't fit a wall in due to a forest or something. Still, the current system is fine in my opinion.
On the point about the line, it seems to be much wider, has a different (less harsh) color, and has some gradual alpha transition.