I suspect that it should not normally be comped for Golds as it wouldn't be an enhanced room in the same category (since this seems to be a separate room category generally costing $20 more per night), but it should be free for Plats if available at checkin from any rate booked on spg.com etc. However, I also suspect that the front desk will offer it as an upgrade only if prompted, just as they generally don't offer an upgrade to an accessible room or suite.