well delta currently has no orders for widebodies with Boeing, do they? All the NWA 787 orders have long since been converted to 737-900 orders, and it seems unlikely they're going to order any 737 Maxes anytime soon.

So yeah, it's technically inaccurate to say Delta is operating an all-Airbus fleet, when was the last time they acquired a Boeing widebody? (hint, it was 2010 - in fact, only 22 of Delta's Boeing widebodies were acquired in this century.)

It wouldn't be misleading to say they're moving in that direction.