The cited study is not peer reviewed, nor does it provide any supplementary data. Simply put, as it is not reproducible, it is not science.

The best studies will be completely open about their assumptions, data sources, approximations, and uncertainties. They generally report (and I find similar conclusions in my research) that in most places where people are buying EVs, given the uncertainties in our supply chain models, they are at par with hybrid gasoline or natural gas cars. And it is difficult to construct consistent scenarios where the electricity grid does not get cleaner over the lifetime of an EV built today and used for 15 years.

A good starting point when exploring these calculations is the GREET model: https://greet.es.anl.gov/.