Unhappy [Q] Bluetooth Media Buttons and App Functionality

I am a recent switchover from iPhone 5 to a Galaxy s5 and need some clarification on how Bluetooth devices and their buttons work with applications both in focus and in background.

I use mapping programs like Waze in addition to Pandora, Spotify, ect and am finding that my car stereo's bluetooth controls don't seem to control the music in regards to play/pause/FF/RW unless the application is in the foreground. Is this the way it is supposed to function or is this a quirk with my S5?

From what I have read it seems like it is a limitation of the way Android handles the media controls, but I would like to know for sure.

I have also found the same to be true when using an LG Tone Pro with Chrome open. You can't control the music unless you either switch to the music app, or goto a menu function of Chrome and the media controls work again. For example, in Chrome open up bookmarks using the three little dots in top right and leave that window open and media controls work as long as this is in focus. Seems odd to me.
In Waze you get the same effect. If you click on the button in the lower left to bring up the menu, leave it open, you can use media controls as long as there is focus.. once you click away it goes away.

Hope somebody can tell me that I am missing something, because this is a real bummer.