Scooters are not designed for Americans, because too many of us do not really 'fit' them. Some Americans do, I guess - and they are the lucky ones IMHO!
At a touch over 6'3", with a 34" inseam, I figured out a long time ago that if I'm going to take up scooter riding I'm going to have to learn to do it with little, or no, extra knee room!
I once took a picture, looking down, of how close my knees were to the front of my Honda Forza. One knee nearly touched, the other had may about an inch of room between my knee and the bar and buttons.
My Burgman 400 had a back-rest thing which could be moved back 50mm or so. (@2") - that was true luxury!
I don't know - at this point I do not think about the knee room thing - I just ride my scooters. If I need to make some kind of turn inside a porta-potty or something - I just move that knee out. No issues....carry on riding.
Shoot - I sat a Metropolitan and a Vino when first looking at scooters - and only did not buy one because the salesman said if I rode a 50cc in Ohio I'd not live long enough to get my pension . (so, I hopped right off!)
Stig