I have the same thing! I think it may take a while to develop a stutter in a different language because at first, you don’t think in that language, you’re translating it to your native language in your head. After a while you think in that language, and that’s when you start to stutter. I’m learning French and at first, I didn’t have a stutter. After a year or so I started to stutter in French as much as I do in English! TL;DR I had the same experience too!