Coming from experience of seeing system releases, albeit not in the same industry, these things happen very often but only gets found out when its very obvious. They would've tested it but I think the pressure of recent feedback meant they made a few last minute changes to bring forward other additions which meant it kicked some other code out of sync that they didn't get time to test extensively. Also, the exotic can be bought by anybody, you don't need DLC to get it. Tldr. It is a bug and the made the best joke possible out of a bad situation.