the pilot came on and said he needed everyone to move to the front of the aircraft (including the flight attendants) to get the CG right for takeoff
For the CoG: The A321 is quite nose heavy, and depending on the your weight and balance policies (operational limits) it might become an issue. A320 and A319 not a concern.
With ACTs fwd CoG does become limiting on A319LR/ACJ.
Standard ops when full fuel with 4 ACTs (28T) with no pax to carry ~200kg of ballast to stay in balance, or if carrying pax to keep them all in the back until TOC.