Good talk! It was surprising to me when I first learned that UPDATE does not literally overwrite what is on disk, its more like an abstracted API that gives me the impression that I updated the row on disk.
Thanks :) The surprises don't stop though - it's abstract turtles all the way down...meaning plenty of fat to trim between UPDATE and what's happening in the MOSFETs. Might be of interest: https://arxiv.org/pdf/2307.11866.pdf
I gave a talk titled "UPDATE Considered Harmful" featuring exactly this idea a few months back. The etymology still makes no sense to me...they should have named it REPLACE instead of UPDATE: https://www.youtube.com/watch?v=JxMz-tyicgo