That clarification is #2 of 2011. The question asked did not raise the point, but the iRB themselves brought it into the mix:
There is a further variable to be taken into account when the ball goes to ground at a collapsed maul and there are players from both sides on their feet bound over the ball so that Law 16 – Ruck becomes applicable.
...
(c) At a collapsed maul there is no obligation in Law for players to roll away unless a ruck subsequently occurs.
So you can't assume that a maul cannot become a ruck - it clearly can. In the England lineout scenario, the maul was formed. The ball was then dropped and hit the deck. This represented the end of the maul under Law 17.5:
[LAWS]Law17.5 SUCCESSFUL END TO A MAUL
A maul ends successfully when :
• the ball or a player with the ball leaves the maul
•
the ball is on the ground
• the ball is on or over the goal line.[/LAWS]
The next question is: what phase of play subsequently exists? The answer is that all the conditions for a ruck are in place. Players, on their feet, are in physical contact above the ball on the ground. So it is clearly a ruck. The offside lines from the maul are retained by the immediate application of the ruck laws.