Summary: Instead of downloading both the forward delta and the backward delta as part of the update, the system computes the backward delta and stores it on disk.
It seems that because they haven't done that until now (keeping the delta to the base locally) they distributed these same otherwise locally computable deltas to every Windows computer in the world with every update!
If I understood it correctly they patented that "approach" and wrote this much (or more) to make it appear more clever and worth of a patent?
"1] The approach described above was filed on 03/12/2021 as U.S. Provisional Patent Application No. 63/160,284 “REVERSE UPDATE DATA GENERATION”"