This doesn't surprise me at all... Just like bots in games. Selling a service that benefits another. Its shady, but definitely believable.
Also, what if this is an actual viable way to "market" for an open source project?
https://www.bleepingcomputer.com/news/security/over-31-million-fake-stars-on-github-projects-used-to-boost-rankings
Well for me personally if I am seeking an application to solve a problem and there are 2 comparable options which are on github, I will first try the one with more stars. Especially if there is a large discrepancy.
When I compare a github vs a non-github project I take into consideration that the other code forge has fewer users, and also I generally prefer devs who take the initiative to get off github. So I will usually give them a go unless the project is too incomplete/stale/inactive.