The switch really is a flag, that indicates that you want the query based on the model to be optimised by the SQL optimizer.
If this is not possible, e.g. because you are using functions that are not convertible, then the flag cannot be obeyed and the query won't get optimized by the SQL optimizer.
You might check on this via EXPLAIN PLAN. As long as you see all the table level accesses you are looking at a SQL engine processed plan. If there on the other hand is a sudden "end" in the EXPLAIN PLAN only pointing to your calculation view, then the SQL optimization wasn't done.
I mentioned it before, but just to drive the point home: "execute in SQL Engine" is not the go-faster switch.
Concerning CE-functions: these really should be avoided nowadays.