In the opening scene of Casino (1995), Sam Rothstein gets into his car and is blown up. In the moment of the detonation, you can clearly see that DeNiro has been replaced with a dummy. (When the scene is repeated near the end of the film, there is no dummy).
While some could claim that this was just a bad cut, to anyone who knows Scorsese, this seems highly unlikely. Watch any interview of him and you will see his attention to every detail. He even likes putting in subtle references to films he loved as a boy. In at least one death scene in The Departed (2006), the actor involved passes crosses made with tape on windows in an abandoned building, a clear reference to Scarface (1932), in which crosses (or X-es) always appear in the background of a scene (either in the prop construction or caused by light falling on the background) when someone is about to die. There are copious examples of this kind of care with detail from Marty. A mistake seems unlikely.
Also, with Casino, Scorsese had one of the largest budgets that he's worked ($40-50 million) with so a lack of money for good effects seems unlikely too.
Q: Has it been revealed anywhere why Martin Scorcese used this scene which APPEARS to be a sub-par effects shot (the dummy) in the film ?
Any answer that can reference Marty himself will of course trump all others. I'm not really after conjecture - I can do that myself.