I doubt they said in court that the Faithful and Discreet Slave does not exist. They probably said the Faithful and Discreet Slave is a theological construct and not a legal person capable of being sued in any common law jurisdiction. If Witnesses want to hear that they denied the Faith and Discreet Slave as a Bible teaching, so much the better.
Sizemik, your comments about being a plaintiff vs. a defendant as requiring different legal strategies and mind sets are so astute. Indeed, they can not sit in the posture of an aggrieved minority religion, akin to Puritan, Pilgrims, and Quakers. They are used to playing David. This case declared that they were Goliath. Whatever the legal merits of the case, it was good for their overdeveloped sense of hubris to be forced to change their policy. All this happened without any court order or direction. A politician taught a legal class that the mere fact of running for office, even there is no chance of election, draws your opponent closer to your policy.
I've attended many a lecture about plaintiff's lawyer vs. defense lawyers duties.