In the Canvas look, a side drawer such as Add domain in Mail opened with a gap above it on pages where the drawer follows the last section of the page. The spacing that starts a new frame below a section no longer applies to drawers, so they fill the full height of the window.
Side drawers reach the top of the window in the Canvas look
In the Canvas look, a side drawer opened below the top of the window on some pages. It now fills the full height.