Story of my life. I remember in high school I would pass this one table during lunch and talk to them sometimes. One day they asked why I only addressed one person when I stopped. I guess I was doing it subconsciously. It had never occurred to me that I did that because talking to one person helped my speak more fluently. To this day it's difficult for me to talk to multiple people, for many of the reasons you mentioned. I also feel like you have put on a bit of a show and need more charisma when you're talking to multiple people. It's almost a competition for people's attention. That's not really a thing for one on ones. I'm already not really a charismatic person and blocking definitely doesn't help lol.