I saw that and another theory on the Smithsonian channel about the low grade rivets used on most the hull's plates. The fire theory is also a good one but I guess we'll never know for sure. I've read so many books about Titanic and so many theories but those two seem the most likely. Other than the bulkhead heights.
I would imagine if they really wanted to the wreckage could be searched and pieces of the ship could be brought up and examined. Examined by experts with today's technology and determine if a "hot long burning / smoldering" fire had an effect on the ship's structure.
My understanding of the current theories on the Titantic sinking are as follows:
1) Because Titantic scraped the side of the iceberg instead of smashing it head-on, too many compartments were flooded for the ship to remain afloat. It was doomed regardless of other factors.
2) What researchers are NOT sure about is why Titanic sank as quickly as it did. Engineering simulations suggest it should have remained afloat for several more hours, providing rescue ships much more time to offload passengers.
Many theories for the ship's unexpectedly rapid sinking have been offered, although (for obvious reasons) it's difficult to find physical evidence to confirm those theories. I suspect many factors influenced the post-collision outcome.