I suppose it all depends on how one defines the word "met," but according to the book
Mickey Mantle: America's Prodigal Son Joe Dimaggio didn't meet Babe Ruth until after Babe's career was over and Joe's was just starting.
Of course, the book could be wrong, too, but the source of the quote was DiMaggio's biographer, so it is likely to be accurate.
http://tinyurl.com/ygx3anz