This shot was faulted because the damage appeared to be caused by the mallet. Later investigation and study of the shot from mobile phone videos proved the damage was by the ball on very soft, wet ground.
An additional Official Ruling was issued in March 2012 following extensive discussion and argument, particularly on the Nottingham site.
The Ruling was distributed to all Australian croquet clubs - hopefully to all referees and GC players. Below is a collection of comments and explanations from various conversations following the issuing of the new ruling.
March 25th 2012
The WCF GC Rules Committee has asked me to issue the following new ruling immediately, regarding Rule 12 (non-striking faults):
"Rule 12 Ruling
The provisions of clause 12(b) shall not apply to a striker during the period
between when the striker's mallet makes first contact with the striker's
ball and when the striker leaves his stance under control"
Is it too simple to say that a non-striking fault (court damage) cannot be committed during the striking period? If court damage occurs from the time the striker's ball is struck by the mallet until the striker leaves his stance under control, then it is a striking fault.
What the new ruling appears to be saying is: "You can't have a non-striking fault during the striking period" I would have thought that that was obvious, and hence I cannot understand why we need this Ruling to tell us that.
It means that any court damage within the specified time window is considered to be a striking fault rather than a non-striking fault as defined in clause 12(b).
All this came because of a request from the English CA following the "Bamford" incident in
the last World GC Championships.
Court damage is always a fault, whether the damage is caused after the
mallet contacts the ball, or without the mallet contacting the ball.
Court damage is a striking fault under Rule 13 [a]  and a non
striking fault under Rule 12 [b]. Note that the non striking fault
includes damage by the mallet, feet or other equipment.
Simply put, it means that you cannot commit a non striking fault
during the striking period.
This ruling is an interim measure and the wording of the Rule will no
doubt be looked at during the Rules review this year.
Court damage under Rule 13 [a]  is limited to damage caused only by the mallet - see the commentary in the Rules Book.
There was an incident at the World GC Championship which was discussed and analysed for weeks after. Considerable damage was caused on soft ground during a stroke, not by the mallet but by the ball. This appears to satisfy the conditions of Rule 12 [b], but is within the time when a striking fault can be committed.
This ruling will stand until the Rules are reviewed and a new edition published next year.
Hope this helps,