This reminds me of a recent experience of mine. I was raised bilingual Greek and English (English is my primary language). For my entire life I heard both of these languages and use them both the same. What I had never heard, until recently, was someone who learned Greek as an adult. I was so excited to speak to them because it was something completely new to me.

When they began speaking (Greek) it was like my brain shorted out. I was so excited for them but it took active mental effort to translate what they were saying. I began speaking to them in English and I nearly couldn't force myself to speak Greek.

This was not elitism or snobbery, it was like my brain decided the path of least resistance was English and I used it automatically. Very strange experience.