The current version has some problems with adaptivity, e.g. resizing the app window can cause issues. This led to the creation of new libadwaita widgets. If you want to read the technical details, see https://blogs.gnome.org/alicem/2023/06/15/rethinking-adaptivity/
What’s the advantage vs. the current version?
Also looks like it’s removing an important visual affordance (i.e., which areas you can click to drag the window), unless I’m misinterpreting it
The current version has some problems with adaptivity, e.g. resizing the app window can cause issues. This led to the creation of new libadwaita widgets. If you want to read the technical details, see https://blogs.gnome.org/alicem/2023/06/15/rethinking-adaptivity/