NB: I wrote this after David Limbaugh's post on the same matter, but unaware of his post.
The Washington Post's Jo Becker uses Judge John Roberts preference of the term "War Between the States" (WBTS) to title the American Civil War as a jumping off point to subtly accuse the Supreme Court nominee of being sympathetic to Southern secession. File this bias under scraping the bottom of the barrel.
While no one that Becker quotes openly accuses Roberts of bigotry or of harboring the view that the 1861 secession of Southern states was legal and the Union's prosecution of war as unconstitutional, hints are dropped that the use of WBTS by Roberts could be a harbinger of a separatist ideology or pandering to opponents of civil rights legislation from the 1960s.
Nowhere in the article is a less sinister, yet equally plausible explanation offered, that classically defined, a civil war is one waged for control of a nation's central government, whereas the American Civil War was a war waged over the question of secession and subsequent independence of one section of the Union, not for control of the central government, hence the more semantically correct label War Between the States.