The thing is you can visibly see how it interrupts Jeremy; he is in the middle of explaining something, then has the face of a surprised person, loses context for a few seconds etc. Better IMO would be if he just finished a small section in its entirety then did Q&A, instead of allowing himself being interrupted all the time. And often those questions are missing the point, which is to be expected with newbies, so the lecture loses efficiency. If I didn't know most of the basics already, I'd have problem following them. I found just doing the exercises better for learning.
I also find the questions very helpful. I understand for many people who already have a good understanding, these questions might be interrupting the flow. Many a times the questions his students raised were things that I had not thought of, sometimes they even stumped Jeremy. Fortunately Jeremy in most cases gives answers which vary in length, according to whether it's a concept which he will clear later, or whether it is an important concept that needs to clarified then itself.
So I think this more effective way of learning/teaching even though there is a loss in efficiency.
Rachel's mic is always off until I turn it on. So if she's asking a question, it's only after she's visually indicated that she wishes to do so, and I've found a time in my presentation that I'm ready to take it. So I'm literally never being interrupted, and can't be surprised by the fact that she's asking a question (although I may well be surprised by the content).
I do try to limit the time I wait to take a question, since I don't want to move on with a topic where I've failed to properly explain some foundational piece.