HaKatan: If your theory has any merit, then what you are describing is simply different dialects or accents. Much like the differences between Yankees and Southern American (or, perhaps, American English and British English).
And neither Southern vs. Yankee (or British vs. American) can be said to be more “correct” than the other. It is simply a difference in dialect and/or accent.
Same idea with the differences in how various Yidden speak Loshon Kodesh. Simply a difference in dialect/accent. One cannot be declared more authentic than another.
Do the Southerners have it wrong or is it the Yankees that are all messed up?