4K resolution
So while 4K UHD sounds like it has a pixel structures with 1/4 the area of 1080p, that does not happen with pixel shifting. Only a true 4K projector offers that level of resolution. That's why "true" 4K projectors cost so much more than 4K UHD projectors with otherwise similar feature sets. They produce smaller pixels, finer resolution, no compromising of detail or color from overlapping pixels. By comparison, the slight difference in aspect ratio between DCI and 3840×2160 pixel displays without overlap is insignificant relative to the amount of detail.
DisplayPort
DSC is a "visually lossless" encoding technique with up to a 3:1 compression ratio. Using DSC with HBR3 transmission rates, DisplayPort1.4 can support 8K UHD (7680×4320) at 60Hz with 30bit/px RGB color and HDR, or 4K UHD (3840×2160) at 120Hz with 30bit/px RGB color and HDR. 4K at 60Hz with 30bit/px RGB color and HDR can be achieved without the need for DSC. On displays which do not support DSC, the maximum limits are unchanged from DisplayPort1.3 (4K 120Hz, 5K 60Hz, 8K 30Hz).