An update from a few months later:
My Batt. Kapa Max values seem to be holding around 15 or so and the other metrics I track seem to agree that there was a bump in battery capacity from the software upgrade. This makes me think that BMW indeed programmed some "conservative" parameters into the initial BMS which have since been loosened up in an update.
That's completely understandable since they were dealing with an unproven technology but they should offer a software upgrade to anyone with an older i3 if that is indeed the case.
I'm open to other theories if anyone has any thoughts?