Comment 6 for bug 1377130

Yes you can get rid of bcache0, but you can't re-use the device for anything unless you reboot ( re bcache or just plain fdisk/parted ).

In fact whether you unmount before stopping the bcache or not doesn't change the behaviour. I did that this way in the description, to show the process.
You just stop the caching device with the echo 1 > ...
But, the backing is still in use and you have no control over it.