That sounds effective, they are probably happy with that bias. If people aren't interested enough to talk to them for half an hour then the outcome will probably be so-so.
I really disagree, it selects people with high tolerance for others wasting their time, so it chases away the most high value candidates.
Even if the selection part is true, it chases away people who cannot be bothered to interact with a human being for 20 minutes or so. High value is a different set of people with unknown intersection.
When I get 10 LinkedIn messages a day, no, I cannot be bothered to interact with each of them for 20 minutes. And since they all refuse to send along any relevant details whatsoever, I can't even cull that to the subset that's plausibly interesting.
No, it is not people who can't interact with a human being for 20 minutes, but with tens of them. If it were an agent / talent model, where it is a somewhat large amount of interaction with a single individual, that would be one thing. But interactively sharing the same information with 20 different recruiters is just a waste of time that has nothing to do with an inability to be bothered to interact with people.