I’m curious to know why these updates have to be so large. There must be some clever way to send only the parts that need to updated, based on the users current version, no?
2.93GB is for the delta update from 11.5.1.
The full version, which doesn’t try to include only the parts that are needed, is 11.6GB.
My understanding, however, is that it’s done on a per-file basis, and any update to a system library invalidates the dyld shared cache… which is a 2gB file all by itself.
These aren't insurmountable limitations, but it seems like Apple chose the path of implementing these in a simple way (at the expense of bandwidth and storage). One would assume they would want to then go ahead and figure out how to implement this with a slimmer delta update, but who knows.