If you can boot your sysNAND using a wupserver image, you can see what I'd expect to be your valid ticket. (It'll have your console ID)But i formatted..
You said that you're using the same NNID on both NANDs, and if you're logged on with your NNID, it should just see that you didn't have a valid ticket on your sysNAND, and ask for one from the server.
What would be nice to do is to recreate this scenario (fresh format, install with fake ticket both with and without an NNID) and check the ticket that's there both before and after you execute the game. If it simply either replaces the invalid ticket, or refuses to enable the DLC, then we don't have to be concerned about fake DLC hurting the system.
Either way, what you saw is how I'd expect a ticket-based authorization system to work.











