wp-includes/class-wp-navigation-fallback.php:212Sorts the classic menus and returns the most recently created one.
WP_Term private static function get_most_recently_created_nav_menu( $classic_nav_menus ) { usort( $classic_nav_menus, static function ( $a, $b ) { return $b->term_id - $a->term_id; } ); return $classic_nav_menus[0]; }Introduced in 6.3.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-navigation-fallback.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.