Yeah, particularly with a smaller audience that can definitely be a problem. I'm better at it than I was a year ago but I still find doing a video without an audience can be a bit challenging. And I definitely can't course correct the way I can if I see a bunch of puzzled expressions in the front row of a room.
On the flip side, you can redo sections and easily insert multimedia and just mix up the talking head format.
The biggest disadvantage was that with a live audience the professor got cues from the audience if we understood him or if he had to slow down. In his videos he constantly assumed he had to repeat everything slightly differently, so you had to watch at 1.5x speed to get to something bearable.