I'm sure you stuck the nozzle all the way in the tank for the pic...but when I gas up I put the gas nozzle by the opening to the tank and fill very slowly, so I can see the gas flowing into the tank. I really don't stick it in at all...kind of 'hover' over the fill...that way I can see the gas going in and see the level of the tank at the same time. Have not overfilled, yet.
Fill hole is too small - by the time I see the gas there - I've probably fueled the evap system.
It's - "add fuel, check w/ flashlight; add fuel, check w/ light; add fuel, check w/ light..."
Not a fun thing to do in a busy gas station.....so, I fill at home.
Vespa owners complain about the same - and a popular accessory is a fill-neck cup to catch your overflow.
Fueling up hassles and the miserable stock plastic gas cap are my only complaints of this scooter after 8 years.
Solved the cap issue with a $12 billet Vespa cap from eBay. See the red cap.....
The fill neck is plastic, the stock cap was plastic - and they didn't like to let go of each other

A common complaint. I posted my remedy on the vespa forum and got much thanks from fellow owners.

Stig