It's not the only model in the upscale process. I never use Nickelback by itself, always with something to depixelize the image before processing. I'll see about uploading some pics of the upscale at that part of the process. Also worth mentioning is people on Discord said they'd prefer more gritty than cartoonish upscales.
Interpolating with XBRDD is generally to bring stability to the model. I'll also make sure to put up some examples of having it upscale the difference image vs using it raw.
Edit: Here's a slide-over comparison https://imgsli.com/ODYzMjI add-proc2 is with the difference mask upscaled with xbrdd-spongebob reloaded. add-proc1 simply used a bilinear upscale of the difference mask. the other two are self-explanatory I think
