Neither wing tip has a particular advantage over the other. If the question is in regard to is one better in knife edge than the other then I would doubt there is any significant measureable much less noticable difference. I would guess they are thinking that the flat tip in knife edge is goint to produce more lift. It would be trivial.

They are getting a placebo effect.

If you are trying to get knife edge working then reduce weight, use enough rudder to get the sideslip on the fuselage large enough to develope the side force on the fuselage, and increase the side area large enough to develop the side force on the fuselage to hold the airplane up.