Yeah I've never heard that before.
What was Manly penalised for this arvo? I think it was Joel Thompson picked the ball up from the back of the scrum. It sounded like the ref was saying that second rowers couldn't pick the ball up, but DCE was in the sinbin.
6 in the scrum, is the rule
When the team has 13 players on the field, it is 6 in the scrum. When there are 12 players, there does not need to be a lock (there can be should the team choose). Think of it this way - There are a maximum allowable 6 players in the scrum, and a maximum allowable 7 players out of the scrum.
As for the Joel Thompson, that is technically true - second rowers are not allowed to pick up the ball and should be penalised for breaking from the scrum early or "Hand in the scrum". The reason for this is the ball can not be played at with the hands until it has exited the scrum, which is defined as the last
row of forwards (though wording probably removed forwards now). The lock can pick it up once it passes the last row of forwards (the second row).