>>34290942Whether it was meant for Pokemon Z is ultimately speculation. Personally I don't believe that they intended Z-Moves to be in some gimmick in a supposed Z version (I don't think there's a precedent for a major core gameplay mechanic to be introduced mid-gen like that), but that they changed the name of Z-Moves at some point in development as a weird kind of fan service to people who wanted a Z version. It seems too coincidental it just happens to be named Z-Moves when it could've been named...well, literally anything else.
People will argue Z actually stands for whatever (Zenryoku or not), but I see no reason they would've happened to choose a word that just happened to start with Z instead of looking for a suitable word after deciding on the letter (IE it's a backronym...lacking a better description since it's just one letter).
At least it's really obvious they changed their plans in some way at some point in Gen 6. I highly doubt that Complete Zygarde was conceptualized as extra content in SM, especially considering how alternate forms for legendaries were handled in the past. Even if you insist it was, the unreleased Eternal Flower Floette is ultimate proof that something changed along the way.