On second attempt, everything was fine. However, I wonder if that is because I already had them imported before, though I deleted the files from the computer afterwards and purged the cache.
I just remember seeing this on occasion before, i.e., that some files show (as is the case in the OP example) and some do not. There was no other difference between files, they are all RAW and shot on the same day, with the same lens, etc.