I think it's fantastic that ED have arrived at the result of 8/12 with certainty, but now that has to be put into the game so that the ingame M61 reflects these findings, much like the GAU-8 was tweaked to reflect new findings.
The M61 ingame doesn't fire 8/12 at the moment, it fires 11.7/17.6 at the moment, as stated by YoYo:
You can find the current ingame values in \DCS World\Scripts\Database\Weapons as Da0 for the M61 series of rounds - they are all set to 0.0022 which as YoYo says, gives 17.5mils when multiplied by 8. The correct value to give 12 mils would be 0.0015 if I'm not mistaken.
As a disclaimer: I'm no expert, and I may be wrong, it's just what I've noticed from some comment in Reddit and what YoYo said