Yup, there are many things that do not add up here. Yes, the sprinklers should have gone off as well as the fire alarm.
The problem here is that the sprinklers and the sensors for the alarms were inside the cabins, while the fire was outside. The glass doors between the cabins and the balconies may probably remained entact, keeping the smoke and the heat out of the cabins, until the side of the ship was pretty well engulfed.
Look at the damage to the exterior of the ship. That metal melted, That is some pretty high temps even if the structure was aluminum.
Melting Point: 660.37 °C (933.52 K, 1220.666 °F)
That's pretty hot folks.
And if it were partial/total steel .... Most steel has other metals added to tune its properties, like strength, corrosion resistance, or ease of fabrication. Steel is just the element iron that has been processed to control the amount of carbon. Iron, out of the ground, melts at around 1510 degrees C (2750°F). Steel often melts at around 1370 degrees C (2500°F).
Yes, there was something involved in the fire that had a VERY high temperature of combustion. The ship's fuel probably has a temperature of combustion that high, but there should not have been any fuel lines in the vicinity of the affected cabins. The explanation of paint, mentioned in Anne's feature article does not add up, either, because this ship is relatively new so the bulkhead should not have had enough paint to burn long enough to heat a reasonable thickness of metal to that degree. It's pretty clear, in any case, that something got ignited that should not have been anywhere near that location.