magento2 – Size filters are not displayed when the configurable product is set to Not individually visible Magento 2

I have this structure for my products, I have a grouped product that has two configurable products which are configured as Not visible Individually but in the filter section does not show any size, if I configure my configurable products as Visible or Search will show the sizes

i use this module to achieve grouped product with configurable products since Magento 2 does not allow it by default

Here is my website

I will appreciate any suggestions. Thank you!