I could not see any hinge or flap or other release mechanism. The connector seems like it is one piece of plastic with no obvious seams although in some images I think tooling marks look a bit like seams. I couldn't pull the cable out with moderate force.
I believe this is the cable that is associated with the connector. It does not appear as though the notch goes inside the connector.
Then just a lot of different views:
The cable comes through a slot in the PCB up into the connector. The connector has through-hole pins on the side nearest the black relays (opposite the PCB edge) *Note the small plastic spur sticking up is from me prying on the connector and not physical feature.
No obvious flange/door or release tabs.
Looks like a single piece of plastic.