The LPI hose does not "attach" to the DSMB the way it does to a BC inflator. Just the opposite. The LPI hose must be held in place manually until you launch the bag. Photo on left is the male end of the DSMB inflator. Is has no groove into which the LPI hose QD female ball bearings can drop. As such, it must be held in place by hand during inflation. When released, the bag takes off. I have never heard of this design malfunctioning (not releasing), but I suppose almost anything is possible in the face of sufficient bad maintenance/incompetence.
Once again, that is why having the connection point out in front of you (by using a long LPI or second stage hose), as opposed to in tight, makes it easier to see/manipulate/keep away from other gear/clutter which could impede/compromise the process. It also makes it easier/faster for bag deployment to be a two person (team) activity.
This is in contrast to the BC inflator male end (right) which has a grove to retain the LPI hose female end.