Yes, some content to be released as Resident Evil 6 DLC is already on the disc, including data for the "No Hope" difficulty and co-op for Ada Wong's campaign. But it's hard to get too angry about the controversy of on-disc DLC when both of those items will be free anyway. Those two freebies will be unlocked (and downloaded to completion) in a free title update soon, Capcom announced.
There will be paid DLC, including timed-exclusive content for Xbox, but that material is not already on the disc. Don't worry, though: if you still want something about Resident Evil 6 to complain about, there's always Resident Evil 6.