Comment by exmadscientist

I concluded that was not possible with this particular model last time I looked, though I should try again (sadly I didn't take notes). It may well have been that the required part was simply out of stock everywhere.

Or it might have been that the lovely, lovely human beings who installed this thing somehow screwed it up so that no extender would ever fit. They had a habit of doing that. Unfortunately, the best way to summarize the electrical in this new-construction house is that Mistakes Were Made™.