They provide links to their github that explains their whole methodology. This is a scientific effort and is as transparent and well-documented as a project can be. They provide the code so you can understand the exact mechanics at play or just fork the project if you want to take the work in a different direction.

It’s a great project and long overdue. I personally think scientific journals are incredibly outdated and haven’t been necessary for a couple of decades. Just put your work on a stable web site and cut out the parasites at the journals.