Actually, Cessna did put winglets on at least one X. But when Russ Meyer got a phone call from his golfing buddies over at Bombardier, the winglets quickly went away. I guess a few years ago, Meyer stated to his Bombardier buddy that the LearJet needed winglets to fly right side up.....and that REAL airplanes don't need winglets (ie Citations). As you can imagine, when the word got out about the X with winglets, Bombardier was quick to call Meyer and question why a REAL airplane would need winglets.
True story? Maybe, maybe not......probably just as much truth as a Citation 12. Also heard that Cessna wouldn't make the 12 unless NetJets would place an order for 150.