I'll guess it's a marketing gimmick, which is to say it has no real benefit over the non-dolby version it must be compatible with for a standard player to play both (surely no-one is stupid enough to pay for two versions of their release or to exclude some buyers by releasing a version that doesn't work everywhere) That means it's basically a tax for a shiny sticker, assuming it's even connected to a physical media.
This is based on pure logic, I've never watched a blu ray let alone UHD
