Restoring bunkers to full strength: WAD?

[HMCS Rosthern]

According to both the old and the updated user manual:

Abandoned Bunkers and Pillboxes can never be restored to full strength once abandoned or captured.

Lower case bunkers can be improved to BUNKER state when they start as lower case bunkers (that might be intended and doesn't necessarily violate the rules).

However, abandoned bunker hexes can be restored to full strength BUNKER hexes as well, which shouldn't be possible according to the manual.

What's the difference between "abandoned" and "vacated"?

the rules say, 

Under Fortifications:
Abandoned Bunkers and Pillboxes can never be restored to full strength once abandoned or captured. 

Under digging in, 
On subsequent turns, based on a probability, there is the chance that the hex will either: • Lose the property of being Vacated, if it was Vacated.