It's not implausible and ridiculous. In fact, in my experience it's one of the most common methods of increasing diversity. Here's a run-down of what my company does (my past workplaces have had similar policies):
* Applications of diverse candidates are accepted from non-traditional backgrounds. In this context, "non-tradition" means majoring in a non-tech field or attended a coding boot camp of some sorts (this applies for non-experienced candidates. For experienced candidates it doesn't matter what their educational background is).
* For diverse candidates, they get two tries at passing the phone screen.
* That said, all candidates go through the same on-site interview loop. The on-site is where the actual evaluation of skills and decision making process is made. This process is not made with any bearing on the candidate's diversity status.
This is a clear example of lowering the false negative rate without lowering the quality of accepted diverse candidates. The false negative rate is lowered by having a more lenient selecting in the first stages. However it's worth noting that these only determine if the candidate move on to the stage where the actual evaluation of skill occurs. The phone screens and resume reviews aren't reliable enough signals for us to make decisions so we only use them to determine the set of candidates that move on the to last stage. Some would point out that this increases the number of false positives for diversity candidates, but that's simply by increasing the total number of diverse candidates. It does not affect the false positive rate. And
The reason why we don't do this for all candidates is because of cost. There's a substantial cost to having full time engineers doing interviews. We already spend ~6 hours a week doing interviews and writing feedback. We couldn't deal with the increased load if we used the first and second points on all candidates. Second, we also want to have larger share of diverse employees in tech positions. Even if people think it's just for better public perception, that's still a tangible and significant benefit.
For what it's worth I think it's perfectly fine way of improving the chances of diverse candidates getting offers. That said, saying that this system is discriminating by decreasing the false negative rate for diverse candidates is an unambiguously true statement and I would object to any of my co-workers being fired for sayings as such.