@BitterJames Hey there! I can clarify what we do with the images for the HWMN release. The digital raws are 1200px tall. We use an upscaler to increase that size to 1400px tall. There are a few reasons for this:
The readability of text on the page is better with a larger base image. While it's only a factor of 1.16, that makes smaller text quite a lot clearer.
Back when physical magazine scans were used, that is the size we used. This is done for consistency. We also update the magazine chapters to scans of the volumes once they are out, where we also use 1400 for consistency. The digital images are already fairly low-quality, with substantial JPEG artifacts. The upscale applies a very light de-noising to the image in order to mitigate the impact of the compression. Digital noise reduction isn't a cure-all, since it's commonly used to remove film grain from video that was part of how the video originally looked. But there wouldn't be digital noise in a printed version of the artwork, or one that was distributed at a high resolution. That is the main reason we treat the images the way we do.
So yeah, we do modify the base image to appear higher quality. I don't think the differences are mind-blowing, but I do think that they come a little bit closer to representing what the manga looks like in print than what the unprocessed digital version looks like. (And the volume versions are much much closer to than than we'd ever get with digital magazine files.) I hope this helps clarify it!