You raise a good point, but at least in my case, I don't think that's what's happening, and here's why. Bias tends to strike and morph into "no" before it ever hits that "getting to know you" phase. There have been plenty of studies about the effect of things like "black" names or gender on the initial screening.
A big part of the hiring process, at least at big companies, is taking a pile of 100 resumes and reducing it to a pile of 10 resumes, because there's no way you're interviewing 100 candidates. So 90% are eliminated before ever meeting, and bias is huge there.
But the bias starts even before that. The pipeline itself is biased. There are more men than women, more whites than non-whites (proportional to society as a whole). This is a problem that needs to be addressed at the society level, not the interview level, but it affects the interview level, because candidates who are "different" lead to unconscious bias.
For older technical people... well, I'm one of them. I'm 53, which means a lot of my social group is the same age. I freely job-hop and don't struggle to find work. I've never felt that my age was a bias against me. What I do see, and I see this a lot, is people my age who worked at the same company for 10-20 years and then lost their job, for whatever reason (usually reorgs or dying companies). Their skill set has become largely about intra-company specialization rather than broad industry skills. I watched my spouse go through this. She lost her job of 13 years in a buyout, and it took her six months to find something else. She had gotten deep in a narrow business field (international e-commerce analyst), and there just weren't many jobs for her, even in our busy town. We didn't want to move to the Bay area or New York, and while she could do generic business analysis or project management, without industry-specific skills, she's not much better than someone barely past entry level. Eventually she found a job that suited her long-built skills, but it took a while. And this story is common as dirt, it's happened to a lot of my friends.
That's how age bias works. It's not discrimination, it's just being unprepared for the job market after too many years in one place. Keep your skills up to date and switch jobs regularly, and age is just a number.
So when you talk about monoculturing and bias at the interview point... nah, that's not the problem point. The problems of bias prevent the interview from happening in the first place.