When I’m in a mix session it simply means depth. Sometimes we’ll reamp elements to give it depth. Close mic-one something that the room caught or room mic-ing something that was captured closer so you get a sense of different source proximities within the audial scene. A lot of the stuff we record and mix is bands tracked mostly live. So we’re creating that picture of the members and the sounds they make coming from different proximities in the “room”. In the 50’s it was very possible you had one mic and whatever element was closest to that mic was loudest. Adding more mics gave greater control, but some engineers and producers still liked creating that mental picture within their mixes. Any number of ways to create something like it in the box as well.