Ethiopian Airlines Flight 503 Operating as a 767-300ER?

According to FlightAware, FlightRadar24, and Ethiopian Airlines itself, the last Ethiopian Airlines Flight from YYZ to ADD operated as a Boeing 767-300ER with a stop in Rome instead of its usual Boeing 777-200LR flying nonstop. But FlightStats says different. For the next flight scheduled in 2 days, it’ll operate as a Boeing 777-200LR nonstop to Addis for the last time. Then on October 30th, it’ll be operating as a Boeing 787 from that point nonstop.

Was the last ET503 a last minute aircraft swap? Why was it? And why is the airline switching aircraft after aircraft after aircraft? I know it is a good idea to be switching to the 787 is because of less fuel cost, and its efficiency.

What do you think?