So I'm turning this over in my brain and I think it might boil down to know your audience.
My audience, the people I'm inviting to my wedding, I can't imagine caring. Most of them haven't done things traditionally in their lives. All of them know, what they are seeing isn't going to legal. Because it can't be in our state. In less something changes in the next year (which is possible, but not probable). So they'll know were gonna sign the dotted line at some other point. Though, in case anyone wanted to know, I love the photo of the couple signing their marriage license so we're going to sign a copy of our vows or something similar so we can get the shot. So we will be signing something that day.
As for secrets. I learned a very long time ago keeping secrets from people you love, who love you back, is just a mess. It's best to be honest. However, I also learned, sometimes it's smart to keep your mouth shut. Which is where we fall. It's not a secret. If you ask "Did you guys get married while you were in California?" we'll say yes, we got all legal out there. But our Facebook status still says we're engaged and we still refer to each other as fiance or as us being engaged. Some people know, some people don't, most don't seem to care.
We actually had a long talk about updating our status on Facebook (yes, it was an actual conversation) and Partner put it perfectly when she said she felt like we were "half married", we're half way there. And well Facebook doesn't provide that option. That's how I think of us. Half married.
Now that doesn't track for everyone. And that's fine. But I think it's important to acknowledge, everyone feels differently about defining what is and isn't marriage. And really, I feel like that's only up to the couple to define. For some people, if you aren't married in a church, you aren't "really married". Well that doesn't track for me. But that doesn't make those people wrong when discussing their own relationships. It's their relationship and they can use whatever language they like.
I will say since we've gotten legalled, I rarely refer to Partner as my girlfriend anymore. She's my life partner now. It's not a conscious effort on my part, but some how the vow of taking her as my "life partner" stuck in my brain. I even have introduced her as "This is my life partner Partner" (and that sentence sounds less weird with her real name and not Partner in there).