Yes, I definitely agree, but it would still seem to reason that one of the top engineers would have considered that. That's something you learn in basic college physics.
You're missing the point. It's not that he didn't know how warp drive worked -- you're taking his words too literally. It's that he'd been approaching the transwarp beaming problem from one mathematical framework, and had become so fixated on trying to solve it that way that he hadn't considered the possibility that a different formulation would be a better way to solve the problem. It's not that he was ignorant of the principle underlying that other formulation, just that he hadn't realized it was a better basis for solving this one particular problem.
Also, remember the setting we're talking about. The Prime-universe Scotty was one of Starfleet's top engineers by the TOS movie era, by the 2270s and '80s, due in part to his accomplishments on the Enterprise
in the 2260s. But the Abrams movie was set in 2258, introducing us to the characters at an earlier stage of their careers, before they'd achieved the things that made their reputations. So this is a younger, more inexperienced Scotty. He's only 36 years old in the '09 movie, and clearly isn't highly regarded by Starfleet Command, or they wouldn't have exiled him to a frozen hellhole.