Chris, Looks even better full length. (The Custom Rifles book is on the way, Thanks.) Sorry but "why" questions about mechanical design are just to complicated to answer here. Try your rifle with a fired case then tell us what happens.
Attached is a poor quality cut-away view sent to me by Dakota years ago.

There is a more than passing resemblance to Martin Hagn's design, (without Martin's approval, including mainspring, sear, trigger and extractor). At one time Don Allan was very interested in my updates, he told me, "Send lots of detailed pictures". Don was well known in the trade for co-opting other people's ideas.
BTW: The company was doing firing pin conversions free last time I checked...
Best, Steve

Hagn Action with external mods.