I'm assuming the bad upload mention of artificial upscaling covers artificial upscales done on existing images but what does this mean for using the tools within the UI for upscaling images already generated then sent to extras?

ESRGAN and similar would probably count as "bad upscaling", the results are not great. Granted, many of the artifacts of upscales are the same as SDs artifacts - that rule is probably a holdover from conventional e6. img2img upscaling and similar basically generate something anew, and they're fine.