I'm not saying it completely eliminates bias by any means, but I've worked at a company growing from 200 developers to 2,000 developers - and getting promoted for me has been a heck of a lot easier than my friends in fixed-size organisations.
When you need to find that many trusted, competent managers that quickly, you can't afford reject people on the basis of their surname :)
I left startup because it was like the worst experience I think I had regarding gender (I am woman). Not that they would be toxic out right as tech bro stereotype, they were not. Generally they were good people.
But the lack of process and inexperience basically amplified the bias. There too much guess work going into decisions, so they were primary based on pattern matching like things. People were making decisions on very little information and in ambiguity, which made all the assumptions matter more. Where while bigger company I am in now, while there are people who openly express sexist opinions, in general I think I am getting more equal results.
Mostly because once they are making the decision, it is more likely to be based on my actual track record rather then feelings. Not that it is perfect, but when it is unfair, it unfair in all kind of various ways toward everyone and it seems more random. More likely based on personality conflict or something of that sort.
When you need to find that many trusted, competent managers that quickly, you can't afford reject people on the basis of their surname :)