A white-labeled surface carries the gallery's identity — its domain, its name in the address bar — while the platform underneath stays out of sight. For collector-facing pages this isn't vanity: the gallery's brand is the product being protected.
The test is the URL bar: viewing.yourgallery.com is white-label; yourgallery.someplatform.com is an advertisement for someone else.
In the product: Viewing Rooms. Related: Online viewing room