Somehow it just doesn't seem right (or possible) that one station could give out 2 different entities like that. I wonder what happens if a station is exactly on an international border-can it count for both entities? It works that way for counties and grid squares.
This one was a real anomaly - like Mike, K9NW said - it must have been during some transition period, when Canton was changing hands jurisdiction wise - it certainly is part of Kiribati now.
Also - before about 1999, the DXCC Rules were quite different and some entities had gotten on the list by some people pressuring the ARRL to change the DXCC rules. There is a lot of controversy regarding how certain entities even got on the list in the first place - and they were "grad fathered in" as of 2000 - but under todays rules, several entities on the current list would not make the cut.
Then there were the controversies way back when - when the ARRL did not even ask for proof that someone actually was at the place they said they activated. There were at least a couple "characters" who had "fake" DX-peditions. That was one reason why the ARRL revamped and cleaned up the DXCC rules in the late 90's.