I understand the pilots are trained to ditch a plane in that area and if there was a fire or the pilot could not control whatever happenig to the plane.... he would set it that way.
There was two piolets talking about this and both confirmed if they had to ditch a plane in an emergency situation it would be the area they’re searching now....with the understanding the plane could have been on auto-piolet for some time....until either it ran out of gas or fire melted the controls.
When it was flying over the Maldives the engines were loud. Partly because it was so low. How far are those islands from the search area?
There’s virtually no chance that such a fire would leave the auto pilot in working order.
The auto pilot and auto throttles will shut off if anything goes wrong and they lose any of the data and sensors they need to operate.