[HKH2]

I don't necessarily disagree, but researchers are not required to be good communicators. An academic can lead their field and be a terrible lecturer. A specialist can let a generalist help explain concepts for them.

They should still review the final result though. There is no excuse for not doing that.

[dasyud]

I disagree here. A good researcher has to be a good communicator. I am not saying that it is necessarily the case that you don't understand the topic if you cannot explain it well enough to someone new, but it is essential to communicate to have a good exchange of ideas with others, and consequently, become a better researcher. This is one of the skills you learn in a PhD program.

[HKH2]

That is how it should be, yes. Do PhDs always meet that standard though? No.