2 of your 3 conclusions are wrong.
It doesn't care what's written to the disc, it's reading at sector level and not file level - so the contents don't even come into it. What it stops you from doing is reading a multiple track / session DVD or BD disc to an image file because there's no way to faithfully reproduce the exact same disc layout.
I think if you were able to see the return codes from the drive as it's 'getting media status', you'd see the drive is having trouble reading the disc.
Switch to read mode and get your unreadable disc ready. Press F8 to enable I/O debug mode and then insert the bad DVD+RW disc. It should log lots more stuff - save the log to a file (using file -> save as in the log window) and upload it so I can examine it.