Several round trips since implemented and all have FC board after preboards and before group 1. Following the new published order
Airports: MSP, DSM, ORD, MBJ, MIA, CLT

Of note: Had to fly Delta for one trip recently and they were inconsistent on the implementation of their new boarding order. One airport still had the 360 customers preboarding. MSP (not surprising) had it correct and there were a few surprised faces in the boarding area