ms101 there could be several reasons.
The aircraft were already fitted with the current seats and delivery would be delayed if they were to be retrofitted. It appears that the aircraft were ready for delivery some time ago but were not delivered.
QR have decided that the 359 should not be fitted with Qsuites only the 35X.
Then there are the politics of the relationship between QR and Airbus! It appears to be a very controversial topic and is best left alone.