In version 3.2.4 we added a new option called "Variation Behavior"
the default mode is actually shown variation product image based on the first image of the gallery. it will replace the first thumb and feature image if there have any image set on the variable field.
The classic mode is a new feature that we have added in version 3.2.4. basically, it'll slide the image based on the selected variation. but it's required to add all same variation product images into the main gallery section. otherwise, it will show the wrong image.
Classic Mode demo: