When I use amazon.com, etc. there's no difference, only when I use domains of competitors or similar sites in my niche
thank you claarky, this is what i mean. There are authorities seperated into niches and this authorities rules and/or is the measure for the other domains. Serps are changing by adding the-domain by rescoring your domain to the next authority.
edit: But this would mean there is no way out of this mess.