Change of Aircraft on QF7 / QF8 ?

[jpp42]

I am booked on QF7 tomorrow 22 May and QF8 returning on 13 June. This is a simple return booking, no other flights involved, booked as classic flight rewards (I have WP status).

The seat maps for both flights show the expected A380 and I am able to choose seats as normal (Premium Economy outbound, Economy inbound).

However I received this notice on my itinerary:

FOR AT LEAST ONE OF YOUR FLIGHTS YOU MUST CHANGE AIRCRAFT
EN ROUTE EVEN THOUGH YOUR TICKET MAY SHOW ONLY ONE FLIGHT
NUMBER AND ONLY ONE FLIGHT COUPON FOR THAT FLIGHT.
FURTHER IN CASE OF SOME TRAVEL ONE OF YOUR FLIGHTS MAY NOT
BE IDENTIFIED AT THE AIRPORT BY THE NUMBER ON YOUR TICKET
OR IT MAY BE IDENTIFIED BY OTHER FLIGHT NUMBERS IN
ADDITION TO THE ONE ON YOUR TICKET. AT YOUR REQUEST
THE SELLER OF THIS TICKET WILL GIVE YOU DETAILS OF YOUR
CHANGE OF AIRCRAFT SUCH AS WHERE IT WILL OCCUR AND
WHAT AIRCRAFT TYPES ARE INVOLVED.

Any idea what caused this notice to appear? As the seller and operator should be the same (Qantas) I don't see why there would be any "other flight numbers" either.

 

[serfty]

E/F reveals nothing untoward with both flights showing 0 stops. Flight status has no unusual info for QF7 - can't look at QF8 yet.

Flight        Stops  Depart             Arrive             Aircraft  Reliability     

QF 7          0      SYD                DFW                388       Unavailable     
                     22/05/19 12:35 PM  22/05/19 1:00 PM             67% / 41m

F1 A0 J9 C9 D9 I9 W9 R9 T9 Z2 Y9 B9 H9 K9 M9 L9 V9 S9 N9 Q9 O9 G0 X9 E9 

QF 8          0      DFW                SYD                388       Unavailable     
                     13/06/19 10:25 PM  15/06/19 6:25 AM             23% / 34m

F8 A8 J9 C9 D9 I9 W7 R0 T0 Y9 B9 H9 K9 M9 L9 V9 S9 N9 Q9 G0