I think the study analyzed the footprint of the person, not the vehicle:

In this new study, the research team investigated whether consumers who purchase and drive such vehicles have a smaller carbon footprint than other consumers

The merits of electric vehicles are irrelevant to their study - and their study is irrelevant to the merits of electric vehicles.

So maybe they’re not lying (or maybe they are, if they made a direct claim about the power mix of the Finnish grid), but they’re definitely far from barking under the correct tree. They’re barking in a different forest, not of transport economy, but of wealth and consumption. :)