Swingarm-mounted engines, guys. That's the biggest thing separating scooters from motorcycles.
Floorboards vs. pegs, displacement, manual vs. auto, all of these exist across all categories and aren't really reliable measures. It's the swingarm-mounted engine.
The Z50 isn't a scooter because it's engine/transmission aren't part of the swingarm (or the entirety of it). It's a very small motorcycle. But it's okay, we scooterists accept small motorcycles, too!