Reports are suggesting that the wrong top cladding was installed (polyethylene core, rather than fire resistant core). The fire code is super complicated (it usually requires that the exact combination of materials and construction method be subjected to a large scale laboratory fire test, or a detailed engineering report from a specialist fire safety construction engineer), but as I understand it, there is no way that PE core aluminium should have been used, and a fire-resistant type of cladding should have been used.
PE core aluminium has been implicated in a ton of high-rise fires in Dubai, Australia, China and elsewhere.
The purpose of the cladding is partly aesthetic, but mainly to cover modern external wall thermal insulation, which was needed to control heating bills (this is mainly social housing, so the occupants are mostly on low incomes) and also to meet energy efficiency code which require energy efficiency to be upgraded to modern standards any time significant upgrades are performed.
UK codes do not require sprinklers or fire alarms in this type of building. This is based on years of experience which shows that they are unreliable (they tend to be vandalised or poorly maintained) and cause a considerable nuisance (e.g. if 400 people have to evacuate because someone burned their toast, or drunk people sound the alarm as a prank).
As a result, the focus of UK building regulations changed from "active" safety (fire alarms, sprinklers) to "passive" safety (non-flammable materials, fire seals, fire doors, sealed concrete compartments, etc.) Due to this construction design, it is extremely rare of for an apartment block fire to spread beyond a single apartment.