> Let's say an interviewer reads your resume and is interested in a project.

That's not what they were talking about. The complex problem is supposed to be novel to the interviewee.

> In fact, silence is encouraged because the interviewer would much rather give you time to think over a spur of the moment answer.

Yes, they certainly say that. But for a normal person trying to figure out a novel problem, ignoring everything that's going on and sitting there silent for 30 seconds or longer while the person who single-handedly can determine whether you pass or fail - often depending on their mood - stares at you is incredibly difficult. And if their mood isn't good, they absolutely see the silence as not knowing the answer and push for you to move on. I had it happen to me on a Facebook interview. I personally can't concentrate enough to think through a difficult, multi-layered problem in that situation. It is in no way reflective of what I can do while working.

Online coding tests are more than sufficient. And a discussion afterwards about said tests is sufficient to make sure there was no cheating.