The immigrant visa is usually a stepping stone to permanent residency via a green card though, and this lawsuit is absolutely related to that process - when applying for permanent residency (green card) on an H-1B, the employer must supposedly prove they couldn’t hire an American to do same job. This is usually called the “PERM process”.
There has always been a gray area as to what that standard means, I’ve seen different companies interpret it very differently. When we talk about employment based immigrant visas and Facebook, it is overwhelmingly the H-1B (the data on visas issued is public).
A green card (I-551) is indeed, not a visa, and I was speaking informally when I described it as such. It is a document that proves the holder is a permanent legal resident, which is an immigration status. The right to permanent legal residence is established through an immigrant visa, such as the EB visas for employment-based immigration.
If you are already in the U.S. on an H-1B visa, your employer will file an I-140 petition for (e.g.) an EB-1 visa. Once a visa is available (this is the long wait for Indian/Chinese applicants in many categories), you can then file a I-485 application for adjustment of status on the basis of the approved I-140 petition. Assuming the I-485 application is approved, then you will receive the I-551 "green card" as proof.
In short: yes, the story is exactly about employment-based immigrant visas.
The PERM process is specifically a prerequisite to an I-140 petition for immigrant visa. Anything assertion that Facebook was "defrauding the H-1B program" is completely spurious.