Yes, the game engine perhaps is 100%, but that doesn't mean all level design was actually finished. Did you see them? I didn't. And nobody I know did. if there were such two disks and they were sent to magazines, they would have appeared somehow. But even if they did exist, they are nowhere to be seen, making this just moot. The fact is that, nowadays, this game probably does not exist at all, and any Amiga nerd wetdreams are just that.
Did the magazine reviews show any proof of levels that are missing in the demo? I don't think so. As far as I know, they just reviewed the demo version. It would actually help if anybody that actually wrote a Putty Squad review back in the day can tell us more information. Anything else is JUST speculation.