It's not 100% of the reason for any one contestant or vote, but it's a pattern discernable across all the series as the numbers mount up.
Personally I do find that the awareness of my likely bias helps me do it less. And I consciously think now, if I have a gut feeling that someone is a bit meh, especially at work, whatever their background, I do a little inner test - what if they just feel different from me? How can I review their behaviour in the most positive light I can? If theres something they do or say that I really cannot get past, that quickly becomes apparent.
And I sometimes think what's the worst that can happen if I over compensate on typically minoritised qualities? I had 2 candidates once for a senior role in my team, they were both appointable, I thought the older white guy was the more credible to me, other members of my team thought the same as me, some others preferred the younger black woman. It was a clear decision to be made. I thought if I go with the woman and she's not quite as good as the guy would have been - so what? I was sure she'd do a good job, she was over the threshold. What's the worst that could have happened? With her, we bring a different voice and set of experiences into our senior team, we provide a greater diversity of role models, yet perhaps some parts of the role are technically not done to as high standard as they would be with the other dude. That's not a bad outcome so let's go with that. Appointing the guy would have meant I lost those other benefits. Who's to say what brings greater success to the team ultimately. Plenty of posh mediocre white people have done jobs that they're not the best candidates for and the world hasn't ended.