Why Don’t Footer Widgets Appear in a Footer Container?

I’m working on a child-theme for Twenty Twenty One and I’m replacing my older footer contents with the footer block editor in the Gutenberg editor.

Rather than go into the Customise menu for the theme, I go to the Appearance/Widgets menu and start there. The editor page indicates this is a footer element in both the editor area and the list view.

My preferred footer layout for desktop is 3 columns of different information and a full-width container underneath containing the site information. Each of the 3 columns consists of a heading and then a list. My logic was to group the relevant blocks for the 3 separate columns which renders as expected in a desktop view. However, instead of appearing within the default theme footer container, the three group containers are nested inside and <aside> tag with a class of “widget-area”. This is clearly a logical way of grouping the widgets, but the <aside> container renders below the #content div container and above the footer #colophon container!

The block editor gives the impression that the user is adding widgets to the footer, but the the rendering does not use any footer elements to contain the widgets. I’m not sure how this works out semantically in the traditional ‘Header/Content/Footer’ layout. The layout renders ‘Header/Content/Aside/Footer’ but I’m not explicitly using a sidebar in the placement of content in pages.

I haven’t made any changes to the core site files in the child theme either. Only the child style.css and functions.php have been edited to suit my requirements.