Ah but that's Twilight. I don't think of her as a scientist. She's a scholar of, among other things, the sciences. It's very different; she reads about what scientists do, she performs clumsy experiments with no thought to control groups or specific hypotheses. She just hooked up Pinkie and got data, with no specific ideas of what she was looking for. She reads it in books and accepts it as gospel; the scientist who studied curses is likely much more open to correction if there turns out to be a real curse.
This is not to disrespect Twilight. She's very good at what she does, which is the practical application of magic and general scholarship. She's very knowledgeable. If I want to know what the melting point of Boron is, Twilight's the one to talk to. However, generating ORIGINAL scholarship isn't her strong point (maybe that's why Celestia has given her the friendship mission; it's something that gets her some friends and social experience AND she can't just find all the answers in a book. She has to reach her own conclusions, not just parrot authorities.)
She just isn't a scientist, much like it's no insult to say that Einstein wasn't a Latin scholar or Bill Gates isn't a philosopher. Their skills and expertise just lie in different areas.