Could you please check how it works with some default WordPress themes like TwentyTwenty or WooCommerce Storefront to understand is it our theme issue or not?
At the moment works, but I don’t know what happend in the future.
Can you do in Portfolio Thumbnails position like in products Bottom (horizontal carousel)?
The portfolio single project is built with Elementor and doesn’t have such a gallery as the product page. That is why this option is not available there.