This is definitely true. Also, it's worth noting that I had to fake the screenshot - screenshots taken in "more space" mode are taken at the res they're rendered at. I took a screenshot of my screen at that res, switched back to "best for retina", put the screenshot full-screen and took another screenshot of that. It looks pretty much the same to me, but there could be subtleties about the live downscaling that the OS is doing that are different when it's a screenshot vs the actual screen.