@Mame,
You know I was talking to our oldest son, a teenager no less and he told me the Apple Airpods will default to the first device I pared them to which was my iphone. So when I use them on my Mac I have to pare them again then it’s pared to the computer, switch to the iphone and it will automatically default and pare the Airpods. Yes technology does suck sometimes. Kids now a days know more then we do! Go figure