Well, your code sample included a step I was not aware of, and incidentally fixed my problem. Also I can reproduce the problem using your sample.
Here are screen captures of the code and the resulting display. I only applied the fix to the "Manufacturers" field in the app. (I've added the pointers to the links for the images, since they don't seem to appear inline. )
Here is my app using the original code which was "broken" or not displaying as I wanted, Image link ->

Here it is with the "fix" Image link ->

Your sample app actually does demonstrate the behavior I was talking about, Image link ->

It turns out to get the text to rest just above the line as desired one has to use the sfTextInputLayout Image link ->

Thanks for the sample, it solved my problem. It's odd that the behavior is this different for the combobox when the separate control is applied over it.
Thank you again for the assistance!
Cheers!