Yes this seems to be a quirk of the booking system rather than any specific entitlement so it would be hard to argue the 'I arrived on an inbound business class flight' when there is no domestic business travel class. (Your World Traveller Plus class ticket booked you in the J fare class, but your travel class remains WT+)
Fingers crossed though you get lucky though as it would be a great start to the trip and it would be good for you to have somewhere to sit down and write your trip report and various posters have reported success. Have a great trip