Weird USB Bluetooth Music receivers

My USB powered bluetooth audio receiver STARTED SHOWING UP AS A MASS STORAGE device.
I DIDN'T EVEN KNOW THAT THING HAD DATA LINES?!?
Did I get rubber-duckied by a BLUETOOTH RECEIVER?
WAIT YOU CAN MOUNT THE STORAGE DEVICE?!?

WTF IF YOU PLAY IT, THE FILE HAS LEGIT MP3 TAGS

OH SHIT I Think this is for it to work on crappy stereos that just play MP3 from a flash drive!!!
To adapt them to work with bluetooth
hm I don't hear anything and the mp3 file exits though
so I guess you need a dumber player that doesn't try to seek in a file
WAIT I THINK I KNOW WHAT THE OTHER FILES ARE
YOU CAN'T PLAY THEM, BUT IF YOU OPEN IT, IT TELLS THE PHONE TO GO TO THE NEXT SONG
so it's used to detect when you pressed previous/next!!! and from that, it signals to the bluetooth device to go back/forward
who the f*** makes this ASIC?!? There's no way this thing is economies of scale