90EX fires when used as Master (it should not fire)

Hello,

I just got the 90EX and I was aware before getting it that it would not fire when used as Master in conjunction with a slave.

I have used it with the 430EX II as slave and any settings I used, both flashes have fired. From the user manual and canon site the 90EX should not fire when used as Master, in fact I don't want it to fire

"When used as Master Unit, the Speedlite 90EX does not fire its own flash during exposure" http://www.cyberscholar.com/canon/camera/index.cfm?page=trainingCenter&product=speedlite_90ex&productPage=mod0301&menu=mod_on3

These are the settings I used:

metering: ETTL - required
Wireless (optical transmission): on - required
HSS
Channel: 1
Master flash firing : greyed out (which makes sense)
flash group: I have tried ALL and A:B (with ratio control) - in both cases the 90EX always fires

what am I missing?