Salvage Files back to extended drive upon media removal

I would like to know why this feature is not available. If a given piece of media is offline possibly corrupt and the extended drive is fine I do not want to delete the files from the extended drive. The documentation seems to define this process as I would expect it to work however it is unavalable when remeoving the media. I am familiar with the DxDmchk utility and it does this as well but it would be nice to enable the option for this on the menu. Is there a reason this is disabled???