I struggle in coding interviews precisely because of this: either I end up vocalizing my emotions and insecurities instead of coding, or I end up coding instead of talking about what I'm trying to accomplish. Often I will see many alternate pathways branching out before me, but if I try to start talking about them, I am no longer coding, and so my brain context-switches to "social and emotional."
Probably something I could get better at with practice, but I honestly end up commenting on places like HN simply because it "allows" me to think. If I could have a coding interview in the form of realtime text chat + code, that would be ideal for me.
I guess I have seen companies do things like "contribute to this open source project and work through an MR." I do find that quite appealing as an interview process.