The QRH says "apply reverse thrust up to the maximum consistent with conditions"
I thought it might be something like that - similar to what I'm used to - I'm being a tad pedantic, but the way I read your QRH is that reversers SHOULD be selected always - the amount of reverse then used should be commensurate with the conditions (speed at commencement of abort / runway remaining / directional control / etc). Idle may be appropriate.
I'm a big believer of doing the SAME actions ALWAYS - the AMOUNT of braking and reverse is up to the PF given the conditions at the time.
IE an abort commenced at 45 KIAS on runway 34L at YSSY doesn't need max braking, spoilers (if you fly a type that requires they be manually extended), and max reverse - but I'll at least apply/select all of them - so it's the same process every time... Hopefully it means I'm ready when it happens at V1-5 on a balanced field!