in Android M can external storage be shared with apps and media files or only apps

I don't have the Nexus player but when I did I tried the early Android M preview build and I was not able to put my media files onto usb storage when it was formatted as device storage. This important to me for portable devices with sd cards. I normally share my music and other files with large apps. I don't want a usb thumb drive sticking out of my phone because I can't put my apps and media together. Thanks! :)