Not only is this another impressive demonstration of incompetence, but by disseminating the idea that people's luggage could be “secure” and “backdoored” at the same time, they're actually destroying what security has existed before. They should pivot to be the “Transport Endangerment Agency”.
In stark contrast with the requirement that TSA be able to open your luggage (unlocked or backdoored), if you declare a firearm in your checked luggage the TSA cannot - by law - have the means to open your [hard-shell] luggage, YOU must retain the key or combination and must be present to open it when inspected.
(Of course, traveling legally with a gun has its own litany of issues, but for those of us who are OK with the basic concept may find doing so helpful against TSA's security theater.)