Thank you Nev - voice of calm reason!
Having spent about 35,000 hours as Cabin Crew and experienced 1 or 2 near disasters & stacks of incidents, I can say most ATPs are extremely deep thinkers trying to weigh up all the parameters and possibilities, not to mention taking calls & instigating check lists, in sometimes milliseconds. Furthermore, you can have all the procedures in the world but there is often a curved ball thrown in for good measure. They use that EVAC phrase with great caution, knowing there are a million things can go wrong. It's a very brave call.
But for the sake of debate...
If I recall correctly, the Singapore Fire Station is almost slap bang where a wide body stops after landing. They possibly have the best equipment in the world. The only speculation I would therefore make is: The Fire Chief called the Skipper & advised him the whole starboard wing was ablaze & spreading, & they would be onsite in 1 minute, & recommended not to evac.
The pilot may have quickly done the sums - minimum 15 second engine shut down + 90 second evac, with only half the exits available, & chance a crew member may shoot off a starboard slide by mistake, versus wait for the storm troopers who would be 60 secs + 10 sec extinguish.... 70 secs v 105 seconds... waiting for fireies was quicker with possibly less risk.
If the above is correct imagine the outcry if he had ordered an evac (& possible disaster) when he had been advised not to!
Mmmm.. mayb not... maybe they simple stuffed up, but got lucky, and I will have to eat my words.
But as with all airline accidents, we will all be wiser in the long run. Like you, Nev, I await with intense interest.