Thanks!
I had assumed [incorrectly] that the reduced write current and the
bit-shifting were tied to each other.  But, instead, it's two
independent techniques for mitigating the same basic problem
when writing of inner tracks.
On Wed, 4 Feb 2015, Chuck Guzis wrote:
  Well, Fred, not exactly--you're correct in that
it's used for innter
 tracks, but RWC/TG43 is a signal INPUT to the drive.