I'm going to speak very candidly, and share that I see this as a difficult question to answer. Where we often have rousing discussions of the 'one wedding per couple limit' on this forum, I feel that answers for or against the additional celebration might be misconstrued as opinions for or against same sex marriage, KWIM?
I see where you're coming from, however I think this is a unique situation that etiquette has to catch up on simply because it is not a situation that could have been conceived of a few decades ago.
Typically, when we talk about "one wedding per couple", the reasons for a couple having more than one ceremony are not because they COULDN'T have a legal ceremony for one of them, but because they CHOSE not to.
In this case, there was no possible way to have a ceremony that was legally recognized, however the HC agreed that that shouldn't deter them from having a ceremony that celebrated their love and commitment for each other. Depending on when that ceremony was, it's entirely conceivable that they didn't think legal recognition would happen in their lifetime. Now that it could be possible, I don't see any reason not to celebrate the legal bond as well.
And yes, for many couples it is also a celebration that they now have the legal rights previously denied them. Again, not something that traditional etiquette was prepared to address but I think modern etiquette can make allowances for it.