That's what I assume as well. Using aspherical elements probably negates the need for more elements to correct different issues.
Probably some of the compactness and simplicity has something to do with the fact that it is a dedicated lens (not interchangeable) which allowed them to put some of the elements so deep in the body. Even behind the shutter as far as I have been able to understand.
Great innovation from Sony, I think they made all the right compromises with this little camera, as far as I am concerned ...