On extractor guns the extractor is one piece to lift both shells simultaneously. On Ejector guns the extractor/ejector is split so the selective mechanism can work for which ever bbl is fired. With the extractor bbls mounted with the ejector forearm, assuming all else is the same if only one bbl were fired then the ejector lock for that side would have to be doing double duty in trying to eject not only the fired empty, but also the unfired shell as well. Not a real good idea. When both bbls are fired then each ejector lock is ejecting only its single fired empty, even though they both eject together.
