"Guessing what a pixel's color might be were one to actually do the work and render it" is not the same as actually rendering it. No, upscaling doesn't count.
Doing it for a whole screenful of pixels, for the majority of frames (with multi-frame generation) is even less of it.
Gamers don't buy GPUs to do rendering, they buy them to play games and make them look good; rendering is just an instrumental proxy to the actual goal of making their games look good. If RTX and DLSS are accomplishing that, who cares how it is done?
Doing it for a whole screenful of pixels, for the majority of frames (with multi-frame generation) is even less of it.