Surfacing I just do not understand when this would ever be something you'd want to do.
Normally I just use edges, sketches or a combination of both.

but if you click a face it will just take the entire surface body as the single line of the direction.  

but what is this? What would the surface body need to be like for this to function as an input? 

Answer:
I guess if you have similar surface bodies or faces you can speed run the creation and kniting of individual boundary surfaces connecting the edges.