The original version is apparently 45GB. I have no basis for saying this (I have not ever worked in the game industry), but my guess would be that this "patch" is really just the complete version that happens to be 11GB larger (which is still significant, but much less than implying there's 54GB of additional content).

Put another way, let's say the actual delta between original and "patch" version is 20GB (11GB new + some changed stuff). There's two ways to ship this:

(1) Create a delta patch file that can be applied on top of the 45GB base version (20GB)

(2) Repackage the entire thing into a complete install (54GB)

If you do only (1), anyone installing for the first time after the "patch" version is released is downloading an extra 9GB and going through a longer installation process.

If you are expecting that only a small percentage of your total install base has downloaded the base game (45GB), it also really doesn't make sense to produce both (1) and (2): You're incurring extra dev and testing time to produce a package that saves you a tiny fraction of your overall bandwidth usage. You also end up with an install base that is partially installed fresh (2) and partially patched (1) which means subsequent updates also have to test both scenarios -- and if you had a bug in applying the patch, you have an even harder time later to try reconcile it for the same reason.

If you do only (2), which is what I suspect this is, then anyone downloading after its release just downloads the 54GB version. The small percentage of people with the initial version have to download an extra 30-ish GB, but it saves you (as the developer) a bunch of testing time and risk.