I reckon there must be some misunderstanding between you and the immi guy. 887 is a permanent residency visa and there's no constraint on where the holders of this visa can stay. I've attached a snapshot of the description of 887 from the official website of immigration for your reference, where there's nowhere that mentions the visa holders have to stay in certain areas, whereas it says this visa lets you stay in Australia indefinitely. It is AUSTRALIA instead of REGIONAL AUSTRALIA!
I hope this helps clear your confusion. Something you might need to be aware of is that the guys answering phone calls at immi are not visa officers and they just have a basic knowledge on the immigration affairs, which means their answers can be wrong where they take it for granted when speculating some issues just according to the way they are called, i.e., regional skilled visa...
Thanks Kelvin...I hope it is this way :)