Australia hasn't played two finger spinners since Sydney 1986- with Matthews and Bright. They played three spinners in total with Holland also in the side.
O'Keefe has two more wickets than him this year at nearly identical averages.
Also don't fail to notice that Ahmed finished the season last year with 48 wickets at 24 and top wicket taker for the SS. While SOK 28 wickets.
A leg spinner would have been good variety and might have been fruitful. Ahmed let himself down on the tour of WI and England by just not playing well enough to be the back up spinner he lost all confidence but he he's come back this summer bowling well.
Although SOK being orthodox may propose some problems and variety. Australia have produced so few orthodox bowlers that Saunders with 14 Tests and 79 wickets is our greatest 100 years ago- our pitches don't help we just can't produce them. SOK has chosen an impossible art to master!