The single-hose pump is the modern pump. Back in the bad old days, you'd often have three hoses--one for leaded, one for regular unleaded, and one for super unleaded. When leaded fuel was banned for sale 25-30 years ago (depending on state), most stations slowly switched from selling just regular and super to regular/mid/super. But most blenders don't actually make a midgrade product, so when you push the midgrade button you're getting a mix of regular and super at the appropriate percentages to give the advertised octane. Some stations even make 4 grades from the two grades that are delivered. Unless you're filling a scooter with a 1-gallon tank, the fuel left in the hose isn't going to make a difference... and if you have a scooter with a 1-gallon tank, it probably runs on anything that burns anyway. Diesel and EtOH blends over 10% get their own hose. American stations often have separate diesel pumps anyway since diesel passenger cars are still relatively uncommon--and look to remain that way as Europe gets on with trying to ban the cars they promoted so heavily just 10 years ago. When I drove diesels in the US, it was always fun to play "find the station with diesel" in a strange city. Europe and Australia just got rid of regular unleaded (RON 91/AKI 87) altogether, so everyone is paying for midgrade even though their vehicles generally don't need it.