I'm not sure why a KVM instance would reference a non-existent cdrom drive. Above, I acknowledged that with the particular options I'm passing, virt-install is treating it as a cdrom. But, as I've indicated, I see this same output on physical hardware with no media in the cdrom drive. I don't have a machine handy that has no cdrom drive at all to test right now, but I believe I've seen the same output in that situation as well.

There is no reason to try and unmount a cdrom drive when no cdrom was ever mounted, regardless of whether the BIOS or installer "sees" a cdrom drive present in the system. It's not being used, so why even try to unmount it? I think this is an artifact from when the use of cdroms was the most common way of installing, and the assumption that a cdrom was mounted just never got updated as installation procedures migrated away from that practice.

"[FAILED]" in red letters may not be a formal "error" in the strictest sense of the word, but it still indicates a problem to the user.

The second message makes perfect sense in some respects. But, there are various conditions (mentioned in previous posts) where this message gets diverted away from the user. E.g., when a serial console is present or the user switches to an alternate TTY, then switches back to the main TTY to finish the install. I haven't tested an SSH-based install to figure out where the message might be displayed in that scenario. In addition, the installer already prompts the user to choose whether to "reboot". I don't have the media necessary to test whether the installer presents the second message only when the attempt to eject the media fails, but if I recall correctly (after many years), various Debian and Ubuntu installers did not present such a message when an optical drive was used for installation and successfully ejected. Back then, choosing "reboot" on the final screen of the installer just worked. I only recall seeing this behavior pop up when I started using USB drives. At that time, this was a fairly new approach, so the messages and extra prompt were just seen as something to put up with. But now it is standard practice to use USB drives, and almost no one uses cdroms.