If the 10 or 12 get the ball off of 1st phase, the defense is perfectly set up and targeting them.
Every playmakers dream is to run onto quick 2nd or 3rd phase ball, with a defense still trying to reset.
This is why we run a 9 ball or 10 ball forward pod. To get over the gainline, perhaps split the defense into two sides of the ruck.
So practically, you want your 9, 10 & 12 to understand that they want the forwards to carry on 1st phase or any time the defense is well set up.
Then you recycle quickly to get the ball into 10 or 12’s hands to let them have a go with their options at a backpedaling or split defense.