The site editor handles content and wide sizes differently than the post editor. Instead of automatic application, you choose which container blocks should respect these width constraints.
Enable content width constraints on Group blocks through the “Inner blocks use content width” setting. This constrains the blocks inside the group, not the group itself – a common point of confusion.
Once a parent container has layout settings enabled, its inner blocks gain access to wide and full-width alignment options. These alignment choices only appear when blocks are descendants of a layout-enabled container.
This gives you precise control over your block theme’s layout system – you can create complex designs with different content widths in different sections while maintaining consistent behavior where you want it.