It's much easier to "explain yourself clearly" to someone from the same cultural/social/... background. Doesn't that approach create a huge bias towards hiring people like you?
Literally every single candidate we get is from a different cultural/social background. I'm not sure why giving them a test first and then interviewing them would make any difference.
Obviously if you ignore the test results then the test doesn't make any difference. But if you assign some weight to whether their solution to a test problem worked (which is culture-independent, or at least less culture-dependent) rather than how well they explained themselves to a person from a particular culture (which is easier for people from that same culture), then you end up with a process that is much fairer across cultures. And similarly for non-culture aspects of a person's background.
If you can't explain yourself then I don't want to hire you. Developers are not sitting in a dark corner not interacting with anyone; they are working with the team, they are gathering requirements from end users, etc.
If you can pass a coding test but you can't express yourself in a way that anyone can understand, then that's a no-hire. If that's a cultural bias, so be it. I don't see how it can be any other way.
Now it's been my personal experience that culture doesn't matter too much. For more than half the team, English is a second language. HR will reject candidates for language reasons even before I get to them.
I'm pretty forgiving -- heck it usually takes at least half the interview before the candidate's nerves settle down.
Being a developer involves being able to explain yourself clearly. You can't just sit in the dark and code, talking to no one. If I came away from an interview with the impression that you can't code then I don't want you. The candidate has to do some work too -- they are there to convince me to hire them, not just pass a test and get a grade.