I only installed 11.3.0 a few days ago. I think it was about 7 GB. This minor update, which I’m only installing because of security fixes for Safari, is almost half the size. It’s going to take an hour to download.
In contrast, the iOS 14.5.1 download – which I’ve installed for the same Safari security fixes – is much smaller.
Question: does anyone know how these updates work, in terms of whether they are at all incremental? Maybe the iOS updates are more incremental than the macOS updates?