Yup, it is. But it is a European distinction because you can buy different packages of the tools here. In America the "Plus" doesn't apply because all tools are sold there in systainers.
Maybe the salesman was referrring to the newer "multi-jetstream" sanding pad versus the older "jetstream" pad. According to Festool the newer pad has better suction. But that update has nothing to do with the "Plus" name.