No, it was never for resort guests only. And that was nice. EVERYONE could watch from there. And the earlier you got there, the better view you could get. I don't know if you are familiar with the deck but it's basically part of the 4th floor concourse, just the outdoor part. It's also how you walk over to BLT. It's a very public spot, it's not a super secret deck like the one at CG if that makes sense.
If I was staying there and came down to watch Wishes and saw this, I would have flipped my lid. Honestly, it would have been enough for me to check out the next day and go somewhere offsite.