I don't know what manual are you reading but if you read Boeing FCOM page 3.20.3 paragraph 2 you will have a better understanding, you can even look at the panel (if you fly 744) and you can see that WAI selector have OFF, Auto and ON positions.
I don't fly for CX.
I'm reading the manual for our 744s. No Auto on the WAI; yes Auto on the NAI.
I flew the 744 until a year ago; now on the -200.