WGT has always said that strokes on the green (using putter) do not degrade your ball...now I hear from several sources that yes, strokes with putter in-game or on practice green DO put wear on your ball, and gimmes put much more than TWICE the wear!
Now headed to practice green with the worthless Lexus ball (1.0 durability) in an attempt to confirm. I so rarely visit practice green... I will be quite perturbed should this be verified.