bearfoil
The "bang(s)" are intriguing.
It is possible that what was heard were two separate sources of sound that happened
(close to) simultaneously.
I agree with you, one bang was gaseous in nature - the stall, the other mechanical in nature, the disc rupturing. If you assume the following: The disc was free on the shaft, it was being subjected to higher temperature conditions than what it was designed to handle, it was rotating at some speed perhaps not approaching what would normally be burst speed (a degraded burst speed margin due to temperature), and the disc all of a sudden is subjected to a huge shock wave of energy (the stall), it might have been enough to push it "off the cliff" so to speak. Rapid P30 collapse - prelude to a stall, engine overheat - a stall - disc failure within ~ 3 seconds. Too bad the CVR of this wasn't available.
When you think about that disc carrying over 100 turbine blades at high rpm's, the load could approach 1,500,000 pounds or more.
It sure would be nice to have seen a photo of the recovered portion of the disc depicting the forward face (we only see the rear face). I say this because we could perhaps see if it is discolored resulting from a fire. There is a hint of this in the photo of the disc fracture surface, but it may only be a shadowing effect from the camera angle and lighting arrangement. Also, the recovered piece doesn't show any evidence of a rim failure.