We could go round and round about terminology ...
But on a library, 'unload' means "take the tape from the drive and put it back in the slot where you got it". that's it. - and that tick box is really "unload", not "eject".
On a PV 124T, you do have to use BE to 'unlock' the library before you can use the front panel of the PV.
When I was using a PV 124T, I had a 5-slot partition for my M - F backup (i was fortunate to fit all my data for each day on one LTO-3). I would remove (with the front panel) each day's tape when the backup was finished and take it off-site.
But, after the Friday backup, I would load all 5 tapes for the next week (a different set of 5 from the first) at one time.
If you haven't checked out the electronic doco with the device, it tells you how to eject a magazine so you can load bulk tapes much much easier than the cumbersome "mail slot".
Cheers