It's just a different (slightly) way to build the delay components into the forward closure. And you can buy different time delays so if you bought the wrong one for your rocket/motor combo you can change it. Anyway thats what I've done with some of them asides from having different delays to play with EX motors using Aerotech cases.
That also includes the rubber delay washer and the o-ring that fits tightly around the delay element. Old style had an o-ring that just dropped down into the delay cavity and sort-of sat there. The new design makes for a definite place for all the parts to go and a couple fewer possibilities of little problems with assembly.