Unfortunately, there’s no way to retrieve the encoding format that was set during the bank building process. I can see the use-case for being able to manually verify the format of encoded audio in banks, so I’ve added it to our internal feature/improvement tracker.
That said, the FSBank API is quite robust and well-tested at this point, so while I’m not discounting your desire the verify the format of encoded assets, it’s unlikely that there should be issues. Are you running into any specific errors with your encoded FSB files?