That article makes it sound like the new narrow bodies are going to directly replace the 50 seat RJs. That’s just not the case. The plan to phase out 50 seaters is on going for all the carriers, but the time frame wasn’t really specified. They will still have what ever RJs their scope will allow. It also said United operates “hundreds of ageing A320-family jets and 737NGs” The new order is 275 aircraft, which is basically a one for one replacement of those older, smaller, less efficient versions of the same plane. Passenger seat capacity growth, but not overall fleet growth.