Definitely do not query the Data Record tables for the storage type in your situation. This can have a domino effect on many processes impacting the performance of the entire environment. I haven't tried to get the Storage Type outside of the Finance Business Rule. In the Finance Business Rule, I can use this Dim objDataCellStorageType As DataCellStorageType = objDataCellStatus.StorageType under DataCellStatus object. Maybe you can get a solution to work using a dynamic UD8 member?
If this is a process that is really needed, then I would suggest submitting a OneStream support ticket and have a discussion with AAS.