Re: ". . . the erase tab as respects the drive/volume into which you're booted? That will always be greyed out."
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That is correct.
I do not have a Recovery Partition on the MBPro HD, so cannot speak to that.
HOWEVER, I made a spare/backup "Install Thumb Drive" of Sierra from the download before installing Sierra on the MBPro. When I reboot in Recovery Mode using the thumb drive, the DU gives the option to erase/secure erase anything that is mounted - internal and external - including the originally installed HD never removed from my MBPro.
Hope that helps.
P.S. This is getting a bit away from the original WIDGET question. Should a new thread be started? Or simply end this sideline at this point?
