In case anyone is following this new magazine issue, I received a response from Daystate. They claim the new mag is fully compatible with the actuator pin in the rifle. If so, the obvious question then, why make a replacement plug/pin that will not index the old style magazine? I'm tired of the issue, and will probably do nothing unless something breaks.
Probably because the unrestricted pin tends to break more quickly? That said when mine broke while I was using primarily the SST I didn't see any performance issue or reason to care apart from being unable to use the original mag.
When I replaced it (no CARM mags at that point), on inspection the pin does appear to act as a guide for itself when intact. I suppose if it binds in some way when broken you might end up with an irritating puff of air from the pinhole on each shot, or something like that.