Waiving a change fee is neither a published, nor an unpublished benefit of GS. If it happens, it's an unexpected courtesy.
If doing an upsell "GG BUYUP" on the same flight from coach to business, it can be waived. I've had it waived as a courtesy when changing to a different flight, but at the same time buying-up to the next class of service. Maybe one or two other times when there was good rationale (i.e. emergency travel -- I was overseas and a family member became ill), but I never count on it.