there is a universal law that you cannot make a slik purse out of a sow's ear - that you cannot enhance beyond what is actually there....

what the TV is doing is overlaying the 1080p onto the 4K - now that is not downscaling in one sense, but it could be seen that way in another

the increase in the number of pixels that the 1080p source can use is a bonus.. but you are still just seeing 1080p, stretched neatly onto a 4k platform so to speak - the subtlety that a 4K original would have is not there because it never was