Do they even release patch notes for things like this?
This is just a theory, but the achievement list was also recently updated with all of the remaining expansion packs achievements that are included with the season pass.
Is it possible that the patch downloads the content to your system, and when you actually "purchase" the DLC through the store, it's merely an unlock key?
I believe they did a similar thing with RE5 Versus on the PS3.
Just a thought.
...yeah, this whole "patch the DLC into everyone's game" thing is not going to cut it this gen when they are this ridiculously big.
If that's what's going on here, it needs to stop.