Quoting from the notes in that zip file:
"Note that most PC floppy controllers have broken single density modes.
Well, that's old hat to me. Around 1988 or so, I suddenly got problems
reading "elderly" 5.25" discs on new PC's. The reason was, that the
160K and
320K capacities were "designed out" of the floppy controllers normally used
in PC's
Nico