Most of the nine groups initially given status are tied to the legal profession; a few were religious in nature. None of the LGBT groups that applied were granted status. The perception clearly is that were not 'enough groups representing both sides'. 

Appeal courts have previously ruled that a key criteria for inclusion is the probative value of the input likely to be offered. Ostensibly Wagner took the view that the position of the LGBT community was already well documented in the submissions before it and, hence, that any additional argument was likely to be redundant. But the public doesn't always understand these nuances; and so as not to give rise to any apprehension of bias, it would have been wiser had some of LGBT groups been included. 

But two wrongs don't make a right. Better the court had issued the aforementioned explanation than to open itself to criticism that it could be swayed by whichever groups shouts the loudest. Its independence and integrity are paramount.