The main reason for the quick fire spread has more to do with the lack of firebreaks behind the cladding which would be a Building Control issue the gap between the insulation/cladding and the concrete face of the building forms a "chimney" for fire if firebreaks are not inserted every couple of metres.
Without this chimney effect the cladding would have burnt out within a small area and would certainly not spread at such an unbelievable rate.
I watched the tragedy on TV with my son who is also a builder and we both realised immediately what was happening.

Many of the deaths could have been avoided if tenants had not been advised by the fire services to stay in their flats and more internal fire escapes had been available.