I have a huge problem with WFH speaking that I otherwise don't in a regular setting - I work at a fully remote, cameras off company and it is very difficult for me to talk in a meeting for longer than a minute without getting that feeling. Just me, in my room, talking to myself. I have no idea if anyone is listening or what they are thinking.
The audience is usually my internal team but I've never once seen their faces in the years I've worked at the company which definitely makes it more unnatural. It's the strangest feeling and I still haven't gotten used to it, but I think you just nailed why I feel like that!