Plus, the 330's got leather covers in Y while the ink was still wet on the merger contract. Fairly new planes, the least offensive to people buying J ticket.
Replace the J seats in the 744 is a no brainier. The IFE system on the 744 is a bit older, they aren't going to reuse it for weight and maintenance reasons. They'll install a newer, lighter, IFE in the entire plane, that means new J seats to accommodate the new system. I would guess the new BE seats are lighter than the WBC seats too.
As an added benefit, that should mean better power for J seats as well. I've never been a fan of the AC power in the WBC seats.