Maybe it is used because the Globe's inhabitants us multiple calenders....just my speculation.
Maybe someone comments at WUWT on the article.
Most dating systems can be converted to Gregorian, and it is predominant. Personally, I use the Unix Epoch for some stuff, but to throw BP as measured from 1950 in there is just an added layer of confusion.
Pet peeve. Sorry. I did like the article.
/johnny