Gutenberg overriding core blocks default settings attributes not consistent

[gsailland]

wp.hooks.addFilter('blocks.registerBlockType', 'childTheme/navigation', (settings, name) => {
    if ([
        'core/navigation-link',
        'core/navigation-submenu',
        'core/navigation'
    ].includes(name)) {
        //console.log(name + ':', settings)
    }
    if ('core/navigation' === name) {
        if ('overlayMenu' in settings.attributes && 'default' in settings.attributes.overlayMenu) {
            console.log(settings.attributes.overlayMenu)
            settings.attributes.overlayMenu.default = 'never' // 'mobile' (default) // 'always'
        }
    }
    return settings
})

The core/navigation block will select never in the editor by default but then in the render_callback, the value is empty ( trere is no overlayMenu key in $attributes ) and the function displaying the navigation Do this:
$is_responsive_menu = isset( $attributes['overlayMenu'] ) && 'never' !== $attributes['overlayMenu'] || $has_old_responsive_attribute;

Shouldn't default attributes to be set? It seems they are omited in the block attributes