save_field

I noticed the MB Builder Extension does generate this code

            [
                'type'       => 'divider',
                'save_field' => false,
            ],
            [
                'type' => 'heading',
                'name' => __( 'Heading', 'your-text-domain' ),
            ],

The documentation for the layout fields does not mention that divider or any other layout field should have 'save_field' => false. Does the lack of this generate a value in the database? Why does the divider field - if generated with MB Builder - come with it, and other layout fields do not?