Reading through the code, I realized that the isRemovable check
returned true when the kDADiskDescriptionDeviceInternalKey property
is set to true. But that sounds like the check needs to be inverted:
According to [1] e.g. a disk is non-removable when it is internal.
And kDADiskDescriptionDeviceInternalKey returns whether the disk
is internal, not external.
I do not own a device with IOKit platfor, so I cannot actually test
whether this patch is correct or not.