Layouts required me to make a change to a bad default decision I made many years ago, and fixing it may visually impact your site.
If you have a site design with a footer that should stick to the bottom even when the page is mostly empty, you may notice the space collapsing with the latest release. The fix isn't hard -- and it is explained in the release notes. So if you see that, please check it out!
Unfortunately, there was no easy way to detect the case so I couldn't just fix it for you automatically. Everyone should double check your site before deploying with this new version. Thanks for understanding!