I think you might get the same results in FileMaker if you turn indexing of your sorting field from <language> to Unicode. I think it might be the key here : ExecuteSQL does not take care about this field settings and will always perform a "Unicode sorting".
You will note numerous differences between the FM usual results and the results of its SQL engine. A big one is that searching (SELECT WHERE) with the later is case sensitive.
I realize that does not help you a lot, but just trying to understand the behavior and conclude i would not hope both techniques to fully match.
Sorry i realize my examples are redundant since if you turn you field indexing to Unicode, then you search will also be case sensitive with FileMaker.