How to modify product data using ProductPageLoadedEvent in Shopware 6?

Does anyone knows to modify product data using ShopwareStorefrontPageProductProductPageLoadedEvent ?

services.xml

<?xml version="1.0" ?>

<container xmlns="http://symfony.com/schema/dic/services"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="SwagBasicExampleServiceAddDataToPage" >
                <argument type="service" id="product.repository"/>
                <tag name="kernel.event_subscriber" />
        </service>
    </services>
</container>

AddDataToPage.php

<?php declare(strict_types=1);

namespace SwagBasicExampleService;

use ShopwareCoreFrameworkDataAbstractionLayerEntityRepositoryInterface;
use SymfonyComponentEventDispatcherEventSubscriberInterface;
use ShopwareStorefrontPageProductProductPageLoadedEvent;

class AddDataToPage implements EventSubscriberInterface
{
    /**
     * @var EntityRepositoryInterface
     */
    private $productRepository;

    /**
     * @param EntityRepositoryInterface $productRepository
     */
    public function __construct(
        EntityRepositoryInterface $productRepository
    )
    {
        $this->productRepository = $productRepository;
    }

    /**
     * @return string[]
     */
    public static function getSubscribedEvents(): array
    {
        return [
            ProductPageLoadedEvent::class => 'onProductsLoaded'
        ];
    }


    /**
     * @param ProductPageLoadedEvent $event
     * @return void
     */
    public function onProductsLoaded(
        ProductPageLoadedEvent $event
    )
    {
        // the product is inside the page object
        $productData = $event->getPage()->getProduct();


        //modifying name
        $this->log($productData->getName());
        $productData->setName('Prefix Product Name' . $productData->getName());
        $this->log($productData->getName());


        //modifying ManufacturerNumber
        $this->log($productData->getManufacturerNumber());
        $productData->setManufacturerNumber('Prefix ManufacturerNumber' . $productData->getManufacturerNumber());
        $this->log($productData->getManufacturerNumber());

        $event->getPage()->setProduct($productData);

    }

    /**
     * @param $message
     * @return void
     */
    private function log($message)
    {
        $logFileName = 'someFile.log';
        file_put_contents(
            $logFileName,
            $message . PHP_EOL,
            FILE_APPEND
        );
    }
}

After modifying the above mentioned changes it still shows the original data although
$event->getPage()->setProduct($productData);

I’m in doubt whether ProductPageLoadedEvent is an after dispatching event or before dispatching the event.