Yes, my understanding (as purely a bystander) is that even the most aggressive fires in the past have allowed time for a mayday. See for example UPS flight 6, with a huge uncontrolled lithium battery fire: https://en.m.wikipedia.org/wiki/UPS_Airlines_Flight_6

In general, onboard fires are one of the most dangerous scenarios in-flight, as I understand it. Crews are trained extensively for it.

I think this is, in part, what the analysis in the article concludes — even a fire would have to cause a very specific, never-before-seen combination of failures to lead to the outcomes observed from the outside.

They should, but there have certainly been aircraft disasters where the pilots didn't exactly do what they were supposed to do.