You're describing low skilled presenters. That is what it looks like when you put someone up in front of a camera and tell them to communicate a lot of information. You're not thinking about "being yourself," you're thinking about how to not forget your lines, not mess up, not think about the different outcomes of the prompt that you might have to deal with, etc.
This was my point. "Being yourself" on camera is hard. This comes across, apparently shockingly, as being devoid of emotion and/or robotic