its just worded badly

what people are saying is

you buy ARR and it says on the box or w/e, requires 20GB HDD space
however all the patch data since 2.0 up to 3.2 has added around 10GB

so now when you buy ARR it will say, requires 30GB, to account for the patch data onto of the base game data

i believe HW already says it requires about 30GB which is why it doesn't "affect" HW

at least thats what I'm assuming people are trying to explain