That's not a reasonable comparison. All other transportation methods are measured solely by tailpipe emissions or energy consumption, like they're some kind of natural geological phenomena. The CO2 emissions for shared scooters/bikes, according to Section 2.4, table 1, additionally include mining and processing the raw materials, manufacturing, shipping over the Pacific, shipping across the entire width of North America on a truck, collection, distribution, and maintenance.
The unmentioned takeaway of this study is how important it is to incentivize improved manufacturing methods that are closer to markets, as well as maintaining existing product (if it's reasonably efficient) to extend service life. Materials, manufacturing, and shipping are responsible for vast CO2 production, largely because there's a strong cost incentive to move that manufacturing to locations with inefficient production and/or loose controls that are far from the product's market. For reducing overall CO2 emissions, improving CO2/KM alone is literally only half of the picture.
The unmentioned takeaway of this study is how important it is to incentivize improved manufacturing methods that are closer to markets, as well as maintaining existing product (if it's reasonably efficient) to extend service life. Materials, manufacturing, and shipping are responsible for vast CO2 production, largely because there's a strong cost incentive to move that manufacturing to locations with inefficient production and/or loose controls that are far from the product's market. For reducing overall CO2 emissions, improving CO2/KM alone is literally only half of the picture.