I think you are spot on with gold plating. The scope has not been changed, rather a developer has added features or made further enhancements that are not included in the project scope.
Scope creep is an increase in project scope that is done without consideration for the impact on cost, schedule , or resources. For example, a construction company is building a new home for a customer. During construction, the customer asks that the insulation be upgraded from standard fiberglass to spray foam. The project manager agrees to the upgrade, but fails to analyze the impact of the change on cost, time, and resources. In this case, the scope increased, but no adjustments were made for cost, schedule, or resources.