That awful thing, upscaling literally FLATTENING the details is still the bane of my life on here.
I even sent a request to staff, some year and a half ago when I noticed this dreadful side-effect. Answer: Oh yes, we are working on it. Well, not.
By the way, it is no better on external upscalers, or perhaps slightly, but still irons out the structure.
I have found a remedy, but that will require an external editor, in case you are interested: what I do is use the HDR functionality, and I add just a little extra HDR structure, plus some extra sharpening. Then reupload the creation. Upscaling will then preserve the structure (to an acceptable degree).