CatBus said:

Basically it's a differences file, which, when applied to file 1, changes it into file 2. This one converts from DeEd v1 to DeEd v2.

It's also an interesting idea for distributing fan edits if Disney starts coming down hard on them. Just distribute xdeltas that convert the Blu-rays to the DeEds. Absolutely no infringement.

I think, in this case, that it doesn't convert DeEd v1 into DeEd v2 (even though this is most certainly possible), but rather from the uncorrected v2 release to the corrected one: v2->v2'.