How does add_option() function enable action hooks to fire right after actiavtion?

The documentation page says that the hook process performs an instant redirect after it fires. So, in order to do something right after the activation the page suggests using add_option like so,

function my_plugin_activate() {

  add_option( 'Activated_Plugin', 'Plugin-Slug' );

  /* activation code here */
}
register_activation_hook( __FILE__, 'my_plugin_activate' );

function load_plugin() {

    if ( is_admin()  get_option( 'Activated_Plugin' ) == 'Plugin-Slug' ) {

        delete_option( 'Activated_Plugin' );

        /* do stuff once right after activation */
        // example: add_action( 'init', 'my_init_function' );
    }
}
add_action( 'admin_init', 'load_plugin' );

How is this any different from,

function load_plugin()
{
 //some code
}
add_action('admin_init','load_plugin');

Won't load_plugin() function run in the same order in both the cases?