You may very well be right, they could also be intended for docking small crafts at the stern. However, in the case of the Fujian, they are affixed to the stern with a large number of thin struts, making it unlikely to have an accessible door behind it like the Nimitz. Passengers from small crafts docked at the stern would have to board / alight via the fantail opening using accommodation ladders or stowaway gangway, but that could be done without such an elaborate structure. So, I still believe their primary purpose is simply as push bumpers or, if the number of struts is an indication, for towing as well.
