Perhaps try thinking before stating the bleeding obvious.
Let’s make it simple for you, old winglets work equally well at low speed, more drag at high speed.

I'm no expert on winglets, but it's my understanding that not all old winglets work equally well at low reynolds numbers. I've heard some factory winglets were quite ineffective so the owners went to 3rd parties. Someone help me out here; I believe I read that some winglets significantly improved the safety of certain models (Ventus? ASW20?) from low speed wing drops. Not a physicist, yet I highly doubt you can accurately measure a 0.25 L/D improvement at high speeds. What method did he use to test? That seems to be well within the noise. (BTW you got docked points for rudeness. It doesn't encourage free exchange of ideas. I'm sure you meant well.)