It's not actually. 9 times out of 10 in these situations mass death is caused by panic and crowd crushes rather than actual fire, so the fire brigade try to avoid that as well as put out the fire. In the case of Grenfell, no one had bothered to tell the fire service about the flammable cheap cladding, so they worked on the standard principle: avoid panic, isolate area of fire, evacuate the necessary, put out fire.
The firemen used the safety advice that helps to save thousands of British lives every year. Its just that in this instance, crucial information was kept from them and the residents, and well, the results were as they are.
JRM is using hindsight to judge and thus is open to criticism.