Einstein's gravitational pull on "further" and "farther"

William Strunk Jr., and E.B. White's The Elements of Style says that a distinction must be made when using farther and further. Says Strunk and White:

Farther. Further. The two words are commonly interchanged, but there is a distinction worth observing: farther serves best as a distance word, further as a time or quantity word. You chase a ball farther than the other fellow; you pursue a subject further.

Their argument is based on, as they say, the disparity between space and time. Yet can't we use Einstein's general theory -- that space and time are inextricably bound in that gravity can manipulate and influence either -- to argue against Strunk and White's postulation that "farther" and "further" are to be ascribed and used in such concrete and distinct manners?