The goal of this question is:

• to be able to interpret WP docs better
• to understand what’s exactly happening in this scenario
• to verify what I’m thinking is correct

I came across this code.

    function register() {
        ...
        add_filter( "plugin_action_links_$this->plugin", array( $this, 'settings_link' ) );
    }

    public function settings_link($links) {
        $settings_link = '<a href="admin.php?page=alecaddd_plugin">Settings</a>';
        array_push( $links, $settings_link );
        return $links;
    }

When I debug settings_link($links), I see $links is an array with a ‘deactivate’ key and value.

Looking at wp dev docs, it seems $links relates to the $actions parameter.
apply_filters( "plugin_action_links_{$plugin_file}", string[] $actions, string $plugin_file, array $plugin_data, string $context )

I noticed though, that the other parameters, $plugin_file, $plugin_data, $context, were not available in the debugger.

I then changed the code as follows.

        function register() {
            ...
            add_filter( "plugin_action_links_$this->plugin", array( $this, 'settings_link' ), 10, 4 ); );  // change 1
        }

        public function settings_link($links, $plugin_file, $plugin_data, $context ) {  // change 2
        $settings_link = '<a href="admin.php?page=alecaddd_plugin">Settings</a>';
            array_push( $links, $settings_link );
            return $links;
        }

Low and behold, now the other parameters $plugin_file, $plugin_data, $context are now available in my function.

I suspect calling add_filter while only passing a callback, is some form of workflow to make things faster & easier.

Can somebody clarify further, or just confirming, what’s exactly happening here?
Is this behavior documented somewhere in the official docs?