see the above video, in the filters appears the sold out product, for example the size 12Y it is out of stock but when you use the filters this product appears, this is wrong something not working correct in your filters and get also the sold out variation sizes
1. Could you please check how it works with some default WordPress themes like TwentyTwenty or WooCommerce Storefront to understand if is it our theme issue or not?
2. Please, disable all external plugins temporarily so we can check what is wrong there.
In this case, you need to create a staging development copy of your website. You will be able to do such kinds of experiments without harming your production website.
You can test it with WooCommerce filters instead. WooCommerce provides this functionality. Our theme widgets are wrappers that add some extra styles but don’t influence the actual algorithm.