[DonVoigt]

The design of the alignment of the trigger lever in the side plate and the sear bar/cut out on the slide do not align until the action is in battery (toggle closed and receiver fully forward) is the "out of battery" firing prevention mechanism, IMO.

The link arm might serve a similar purpose under some conditions; but as pointed out by Doubs, if the sear is released from its catch, the normally strong spring will also close the action when the striker moves forward. The striker may or may not have sufficient energy at that time to activate the primer.