There's a difference between sacking a city and razing it to the ground.
End of Myles's quote
In terms of "We, as a nation, does not care for this city at all anymore and will cease any support immediately. Anyone living here will be relocated and/or killed"; No, not really.
That doesn't destroy everything though. Maybe if it's a small city than yes, you could just burn down the huts and other small buildings which would probably be made of wood. But in a large city there would be walls and buildings made of stone, which aren't so easily destroyed.
End of Myles's quote
While entirely true, in the context of what we want to do - remove any and all support from a city and basically take them out of the proverbial equation - "Razing" a city is ridiculously easy. Especially as an seemingly omnipotent despot.