That's not my experience -- there's a whole pretense about being experts in a field, which is exactly what the poster above bought into. Having a PhD doesn't make or prove you're an expert about anything. It just proves you know how to do research in a thing, but that doesn't stop us from presenting PhDs in front of juries as if they're the only ones who know what they're talking about.
I don't see how these are incompatible. The PhD prepares you to be an independent researcher. The way you prove this is by studying the same topics for a few years, and by the time you reach your viva, you'd be expected to know a lot about the topic you chose.
It's not incompatible, many people in order to do research have to gain a great expertise in a thing. Others can get a Ph.D. having really no expertise at all, but just the ability to get through a research program. Others still can be experts and unable to navigate a research program due to how capricious and political they are. So the pretense is that the Ph.D. is a marker of expertise. It's correlated with expertise, but the actual thing it signals is you've gotten through a research program.
