That was pretty specific to the DC-10: A money-driven design decision had the cargo door open outwards to allow more cargo to fit inside. A design flaw meant that it was possible to close the door without fully locking it.
so therefore locking becomes irrelevant. even if some crazy person goes up to the doors mid flight and tries to disarm, unlock, and open them, they simply won’t open when you’re at altitude, even though the aircraft is pressurized.
long story short the difference between closed and “locked” is actually almost irrelevant in modern airliners when the aircraft is at altitude.
The DC-10 eschewed this standard in favour of doors that opened directly outward with catastrophic results if the locks failed.