We try for a finished product as close to 5 oz as possible. This weight will vary across the Shell and weight falls off towards what was the rear of the hide. It is not impossible to see a 2 oz difference from one side of the shell to the other.
Corrected grain leather refers to leather that has grain that has been either partially or completely removed by a buffing (sanding) machine. There are different grits, papers, machines, and pressures that are used to achieve a very wide range of results. How the leather is finished will then determine what the surface looks like and how it performs.
I'm digging up old posts from months ago, but we do not have a "ghost writer" doing any of the media that you read and Shell Cordovan is technically full grain, at least the way we do it. The grain is left intact though it is the flesh side that becomes the finished product. All of the flesh is removed away to expose the shell which lies within the hide.