Connecting via Android Auto, still plays on my desktop

[scottaronbloom]

Plan

Premium

Country

USA

Device

Samsung S10+/S9+/S8

Operating System

Android multiple versions/Windows 10

My Question or Issue

When I am listening to spotify using the Windows Desktop application, and not through my phone, everything is great.

I move to my car, and plug the phone into android auto.  Hitting play, starts playing it on my desktop.  I have to go into the app (i cant make this change via the android auto interface), and select the phone as the device..

I would assume it would auto select the device that is connected to the android auto via usb... What am I doing wrong?