Update
So I booked a mileage run for over 6000 miles which I completed on Dec 13th. Looking at my account today (Dec 15th), everything has posted plus the 3000 AMEX bonus status miles.
The weird thing is that I'm sure that my membership year was Dec 15th to Dec 14th, yet the 3000 posted on Dec 15th got added to this years balance.
In any case, the BMI site doesn't show the membership year anymore. Have there been any changes to the membership year concept?