Apparently not. I actually went and tried it before I read the rest of the comments here, which verified my results. My habits seem to have masked this; I use Calibre over USB to put side-loaded documents on one of the Kindles and don’t ever try to read them on the others. Turns out I get most of my fiction from Amazon via BookBub and my sideloads are mostly non-fiction. I apparently read non-fiction on just that one Kindle and my desktop, fiction on all the devices. I guess it’s a matter of reading purely for pleasure in a big comfy chair vs somewhat more serious reading.
I really need to switch to email uploads from Calibre; the sideload Kindle is approaching being full. My Internet connection is gigabit, so it shouldn’t be much slower. The Travis McGee collection is all sideloaded, but I only allow myself to read it once a decade, so I have awhile to fix it.
