I think it must be 2 decades since I had to use a special utility to load MP3s on my phone. Even my Kobo reader will just work with any old EPUB I copy onto it. By all means generate metadata to improve the experience but let it sit alongside, preferably in *my* carefully named directories rather than buried in arbitrarily numbered folders. Not that I could get a connection to the companion more than once (and even then it wouldn't download any images).
It's a shame because the viewer itself is excellent, though to my mind the controls are inverted - maybe it's a gaming thing but I kept expecting the stick to move the viewer rather than the subject.