OSX-formatted USB drive giving strange partition message when I attempt to eject it. "Boot OSX" hidden partition?
This EFI partition is discussed at :
https://discussions.apple.com/thread/4326715?start=0&amp;tstart=0
The opinion there is that it is created by (some versions of) Time Machine.
Disk Utility hides it by default, but see
https://www.mede8erforum.com/index.php?topic=14019.0
for how to show it and remove it.