Yes, it is difficult to understand indeed. The title says: "A Gift to you: additional award miles". Hence, I also understand that additional award miles would be credited. But I actually got none (neither additional miles, nor credit of due miles on past flights).
On another note, I am sometimes credited with award miles in the same amount as status miles for certain of my flight legs. The new award miles system is completely unpredictable and the award miles posting cannot be understood, as far as I am concerned.
M&M should roll back to a system that users can understand. In addition, the old system took into account the margin made by the airline, as higher booking classes (those with higher margins) yielded more miles. In the new system, the credit of award miles only depends on $ spent and ignores the margin. If M&M wanted to spend less award miles, it could have even cut more the yield on the lower booking classes.