Technically, by that logic, wouldn't the Magic Kingdom be a studio, too, since many of the rides there are themed to movies, too? And speaking of, how is it that Splash Mountain/The Princess and the Frog requires justification for it being in Frontierland, while it requires no justification if it were in Fantasyland?
And I don't remember too many Disney history books calling "Snow White" the world's first full-length animated studio. It's the world's first full-length movie.
How is it that the Studios requires no explanation whatsoever when it comes to ride theme, but all the other parks do, as far as fans are concerned? And no, I don't think just the fact that they're movies is good enough.
If they're going to use the name of "Studios", then it should be used in the more literal sense. Even Universal Orlando still uses its facilities for filming once in a while, even if it's not anything worthwhile, like the Powerball or wrestling, so Universal wins the actual "studio" name theme battle by default.