I sincerely hope your friend is just fucking with you regarding this.
The idea of using your phone for basic features on Switch and thus consuming the battery of both devices at the same time for something that could be done on one could backfire in a big way.
Ah you got it in time. Like I said it's heavy speculation on my part anyway, but based on solid info. My friend isn't fucking with me.
Edit: you have no idea 🙃