Product variant URL with attribute and value IDs: doesn’t switch image to selected one

In magento 2 is possible to call a specific product variant just appending to the “normal” URL:

#Attribute_ID=Value_ID

I’ve read in various posts that this functionality should also involve the switch of the image to the selected variant (for example here).

But does anyone know why in my shop Magento 2.3.6 this doesn’t happen?
The attribute inside < select > element correctly shitches to the variant, but the image remains on the first one… it could be related to the theme?

Thanks in advance to those who will respond!