I’m genuinely curious. Other changes are just following modern (and stupid) trends so nothing weird with that. This one though just makes the maximize, minimize and close buttons look smaller than others (new tab in Console etc) which imo creates inconsistency. Also it may not apply to all display resolutions but it does on mine.
All extensions are disabled. I use the adw-gtk3 theme for GTK3 apps but I’m not talking about those (though the latest version of the theme also has smaller buttons that means the GTK devs probably have indeed changed the size of the buttons).
On the screenshot there is a GTK4 app that hasn’t been updated to the newest libadwaita version (Pipeline) on the left, and on the right there is a default GNOME app that has been updated (Console).