The line between scooter and motorcycle performance is a narrow one and sometimes overlaps. The larger scooters can tour better than some mid range motorcycles.
But, the definition of a scooter, as far as I understand it, is a step through design. You can argue about other things but that is the one difference, and it gets muddied, like on the Burg's. Are they really step through or just kinda
There are now motorcycles with a drivetrain from a scooter. "Gas tanks" are now storage compartments and gas is under the seat (like some scooters). Automatic trannies are more common on bikes now days.
So, what is the real difference?
I don't care if someone calls my motorcycle a scooter. Heck, sometimes I refer to the Guzzi as my scooter.