Is a starter a dough, or what..as to method of forming?

I am using Peter Reinhart's "Crust and Crumb" to make the Pain au Levain.  I am curious as to why the mild starter does not get a 20 minute rest after first being made into a ball.  

Also, I used this method of hydrating the dough...Weigh, then sift, the flour.  Put it in a large bowl and make a hole in the center.  Sprinkle the water around the dough and into the center.  Then, I rotate and swivel the bowl until the moment when most of the flour has hydrated and some is left over that won't join in.  Then use my hands to form the ball.  

How much glutenizing goes on in the first starter?

Comments welcome. 

Dan, NYC