DERG
Howdy. Rather than dredge up my old posts, I'll rephrase and update. The "Pipe" is NOT the victim of some inattentive Bench Monkey.
First, notice the "Land", or "Ledge" that supposedly resulted from a "counterbore" gone awry. Look closely at the "corner" enunciated at the transition from ledge to Wall.
It is COVED. It shows no sharp delineation twixt the bore and the "Shoulder". This is 100 per cent the result of wear, and given its locale, almost certainly caused by vibration.
Next, note the Striae on the wall of the inner surface of the "normal" pipe. My opinion is a pulled extrusion process assuredly excluding any secondary operation, or Blunder. Gently Helical signatures from a normal process of machining. Now, look at the area of the Pipe proxima; to the "ledge". There are circumferential grooves, the result of metal/metal wear, as this is undoubtedly the joint locus of two fittings. Look closely and see that the grooves are at bias to the ledge, and irregular, random even, and certainly not the result of any machining process.
There is a great deal more. Suffice that ATSB allowed for a wide open gate for later correction: "....MAY have initiated a sequence of failures that led to burst...."