Allocate Points in Bulk.

function allocate_signup_points_to_existing_users() {
    $args = array(
        'role'    => 'customer',
        'orderby' => 'user_registered',
        'order'   => 'ASC',
        'fields' => 'all_with_meta',
    );
   
    $users = get_users($args);
    foreach ($users as $user) {
        $signup_points = 100; // Replace with the number of points you want to allocate.
        WC_Points_Rewards_Manager::increase_points($user->ID, $signup_points, 'signup-bonus');
    }
}

// Run this function only once, then remove it or comment it out to prevent it from running again.
// allocate_signup_points_to_existing_users();