Given the repeated tendency of commercial pilots eg. Korean 007 or Iran AIr 655 to to aggressively pursue missiles and insist on colliding with them, it is understandable that military authorities in every country will insist on short and clear investigations when they serve their political masters
I don't think there has ever been such a thing as an honest investigation after a missile shootdown of a civilian airliner, nor can one be expected. The investigation after the Iran Air 655 flight was probably the best one can hope for, and the facts, or at least a fairly plausible version of the facts slowly emerged after a long time and retirement of all concerned.
Edmund