Hey there @ahmet welcome to the forums.
If I understand things correctly, when you provision a BeagleBone Black, the image that you flash on to an SD card then installs the OS onto the eMMC on-board the device. It’s an image that then flashes the internal storage of the device.
I’ve never tried this but what you potentially need to try here is to ‘unwrap’ the image after downloading it (before flashing to SD card), to extract the OS image component that’s inside it, then flash that to an SD card. That way balenaOS should run directly from the card like it does on a Raspberry Pi (as you say).
We have a tool for doing that, although I can see it’s quite old, but it would be worth a try: GitHub - balena-os/balena-image-flasher-unwrap: Tool for unwrapping balena-image from a balena-image-flasher (unless you can find another way).
Hope this helps!