I'm sure there are more educated people than I that can give you a better answer but I believe the 12 star variant would have been standard issue flags from the department of Alabama, Mississippi, and East Louisiana. These flags were issued from the Mobile depot. Forrest's units did receive such flags and became associated with him. Check out the museum of the confederacy's flag database as well as Alabama's fantastic digital catalogue. There are numerous examples of the Mobile Depot style flags.
Best!
Drew