That's the one I'm talking about. The left-most button is the automatic update, the button to its right downloads the entire install instead of just the changed files.
For those who can use the automatic update, maybe they are receiving a smart only-update-the-files-that-changed. I wouldn't know, as I'm stuck doing it manually. I suspect that if the only a few files have changed and someone complains that "it completely stripped away all of my modifications that I had coded in" then either all the changes that person made was in the few files changed or all the files were refreshed on the automatic update.
I haven't made any core changes, however, since I suspect automatic updates are brute-force instead of incremental-based, the manual update would be safer for those who have made core change edits and want to preserve them, but a list of changed files makes the manual update go faster.
We'll see how it goes next update. If the list of changed files isn't posted at the time of the update, I'll be going through the same process of hunt-by-date.