Wrapping the item that appears in your inventory after swapping the herb with an item in the gbank is normally wrapped because it is the actual item, so you gain nothing by doing so, unless there's a way to move the item in the gbank.
Also, milling 5 bugged herbs changes nothing, doing the trick on that also changes nothing I believe.
EDIT: Quicker method:
1. Separate a 5 stack from the 20 stack (have 15 and 5), also have another stack or just loose herbs
2. Mill the 5 without looting
3. Add a single of the loose/other herbs to the -now greyed- 5 stack (should no longer have "5" on it)
4. It should no longer be grey, close the loot window and you should have a bugged herb
This is the same as before, ignoring the step of picking up the 5 stack and placing it on the original stack. From what I tried this works in the same manner.