Does it? I just switch thinking to another language, it's not a big deal (as long as you have reasonable fluency). I thought it was reasonably common (all the people I spoke with about it seem to do the same)
When I'm reading HN I think in English, when I talk with my team I think in English, when I talk with my girlfriend or go grocery shopping I think in my native language. It's difficult to use both languages at the same time, but it's rarely the case (e.g. I might continue speaking English and not notice when I started a conversation in a multinational group but then I talk to someone I can speak a more suited common language with) . In terms of work I do, I think I'd struggle with my native language more, as there is no equivalent terminology and I'd have to use English anyway.
Picture trying to do some fine work while wearing thick gloves. You are not going to perform at your maximum capacity.