But honestly your question makes me suspicious, because I have had a client bring on a few people into a project (who I was not able to check beforehand) who abused this asynchronous thing.
One was just QA person who just had multiple jobs and would literally have a different and creative reason she did not have time to finish her work every day. It could take a few days for her to get back to you even if she appeared to be idling in the server. Then with the excuses.
Another was an American scammer who claimed experience with just about every technology, and pretended to be working on "wireframes". When we complained too much that he wasn't available to discuss things, he supposedly started showing up in the chat room. But strangely his answers were quite short and sometimes somewhat broken English. I sort of tolerated it for a week or so because I was really busy doing my part. But then we were supposedly having a call to discuss the actual details and amazingly he seemed to have no problem talking about the project for several minutes without ever actually saying anything specific to the project.
So on that call I insisted that we discuss it, and asked him a specific question about the core technology. He could not think of another way to evade the question so he left the call.
Anyway he eventually admitted to hiring some overseas person to "work" on it, and that was the person who was sitting in the chat room. (Although not really saying or doing anything useful).
Having said all of that, I think video calls are usually unnecessary, and text chat should be sufficient 95% of the time.