The redesigned cumulative updates for Windows 11 have an approximate 40% reduction in size resulting in both a faster download as well as installation. I certainly noticed the difference with the latest Insider Build as it was the fastest new Build install I've experienced to date!
An overview about the changes is available at Windows 11 cumulative update improvements: an overview (https://techcommunity.microsoft.com/t5/windows-it-pro-blog/windows-11-cumulative-update-improvements-an-overview/ba-p/2842961).